Learn Hardcore Croatian: Večeras ću povesti djecu u park. - Tonight I will take the children to the park.

Croatian has a rule that short unstressed words called clitics (like ću, sam, se, ga, mi) normally stand in second position in the sentence or clause.

In Večeras ću povesti djecu u park:

The first element is Večeras (tonight / this evening).
The second position must be filled by the clitic ću.
Then comes the main verb povesti and the rest.

That’s why it’s Večeras ću povesti, not Večeras povesti ću.
You can say Povest ću djecu u park večeras, where povest is first, and ću is still in second position.

What is the difference between povesti, voditi, and odvesti?

All are related to taking/leading someone, but with different nuances:

voditi – imperfective: to lead / to take / to guide (ongoing, repeated)
- Vodim djecu u park svake subote. – I take the kids to the park every Saturday.
povesti – perfective: to set out taking/leading someone (starting the action, single event)
- Večeras ću povesti djecu u park. – Tonight I’ll (set off and) take the kids to the park.
odvesti – perfective, usually by vehicle or emphasizing the result “get them there”
- Večeras ću odvesti djecu u park autom. – I’ll drive the kids to the park this evening.

In your sentence, povesti focuses on the single action of taking/leading the children somewhere this evening.

Why is it djecu and not djeca?

Because djecu is in the accusative case, used for the direct object of the verb.

Dictionary form / basic plural: djeca – nominative plural (children)
Accusative plural: djecu – used after most verbs as “whom / what” you are acting on

You can see the pattern:

Djeca se igraju. – The children are playing. (subject = nominative)
Vidim djecu. – I see the children. (object = accusative)
Povest ću djecu u park. – I will take the children to the park. (object = accusative)

So povesti koga? – djecu.

What is the singular form of djeca, and how does it decline?

The singular is dijete (a child). It’s irregular, and djeca is its plural. Basic forms:

Singular:

Nominative: dijete – a child
Genitive: djeteta
Dative/Locative: djetetu
Accusative: dijete
Instrumental: djetetom

Plural:

Nominative: djeca – children
Genitive: djece
Dative/Locative: djeci
Accusative: djecu
Instrumental: djecom

So in your sentence, djecu is the accusative plural form of djeca.

Why is it u park and not u parku?

The preposition u changes case depending on meaning:

u + accusative → movement into / to a place
- ići u park – to go to the park
- povesti djecu u park – to take the children to the park
u + locative → location, being in a place
- Djeca su u parku. – The children are in the park.

Your sentence expresses movement towards the park, so accusative is used: u park.

Could I also say Večeras vodim djecu u park? Is that different?

Yes, you can say:

Večeras vodim djecu u park.

Difference in nuance:

Večeras ću povesti djecu u park.
– Uses future tense
- perfective verb (povesti).
  – Emphasizes a single, planned action that will occur this evening.
Večeras vodim djecu u park.
– Uses present tense of voditi (imperfective).
– In context, present can also refer to the near future.
– Sounds a bit like talking about your plan or schedule: “Tonight I’m taking the kids to the park,” similar to English present progressive.

Both are correct; the future form can sound slightly more “formal” or explicitly future-oriented.

Can the word order change, for example: Dj e cu ću večeras povesti u park?

Some changes are possible; some are odd. Here are examples that are grammatical and natural (with slightly different emphasis):

Večeras ću povesti djecu u park. – neutral, common.
Večeras ću djecu povesti u park. – mild emphasis on djecu.
Dj e cu ću večeras povesti u park. – emphasizes djecu (not someone else), but still acceptable in the right context.
Dj e cu ću povesti večeras u park. – also possible; the focus changes slightly depending on intonation.

What doesn’t change is:

ću stays in (or very close to) second position in the clause.
The meaning remains largely the same; word order mainly affects focus/emphasis.

Is večeras a noun or an adverb? Why doesn’t it need a preposition?

Večeras is an adverb of time meaning this evening / tonight.

As an adverb, it behaves like:

sutra – tomorrow
danas – today
jutros – this morning

Adverbs don’t need prepositions or case endings:

Večeras ću povesti djecu u park. – I’ll take the kids to the park this evening.
Sutra idem na posao. – I’m going to work tomorrow.

So no preposition is required before večeras.

How do you pronounce ću, and what is the difference between ć and č?

Ću is pronounced roughly like “choo”, but softer than English “ch”.

Difference:

ć – a soft “ch” sound, tongue closer to the front of the mouth
č – a hard “ch” sound, more like English “church”

Approximate:

ću – softer, like t’yoo with a light “ch”
ču – harder, like choo in “chew”

Minimal pair:

ću (from ću / ćeš – future of biti)
ču (from čuti – “to hear” → ču = “I’ll hear” in colloquial speech)

In your sentence, it’s the soft one: ću.

Can I say povest ću instead of ću povesti?

Two separate issues here:

Position of ću
- Verb + ću: povest ću djecu u park
- Time word + ću
  - verb: Večeras ću povesti djecu u park
Both patterns are common and correct; ću just needs to be in the second position of the clause.
povesti vs povest
- Standard infinitive: povesti
- Colloquial shortened form: povest

In standard written Croatian, you usually keep -ti or -sti: povesti ću / ću povesti.
In everyday speech and informal writing, you often hear/see povest ću instead.

Why is povesti (perfective) used with ću, and not voditi (imperfective)?

In the simple future tense, Croatian typically uses:

future auxiliary (ću, ćeš, …) + perfective infinitive
when talking about a single, completed event.

Examples:

Sutra ću pročitati knjigu. – I will (finish) reading the book tomorrow.
Večeras ću povesti djecu u park. – I will (take) the children to the park tonight.

You can form futures with imperfective verbs too, but they often sound more like:

a longer or habitual action
a polite / formal future

So povesti fits naturally here as a single, bounded action planned for this evening.

Could you ever say na park instead of u park?

For park, the usual preposition is u:

u park (accusative) – to the park
u parku (locative) – in the park

Na is more like “on / onto / at (an open surface or area)”, used with words such as:

na plažu / na plaži – to the beach / at the beach
na stadion / na stadionu – to the stadium / at the stadium
na koncert / na koncertu – to the concert / at the concert

With park, native speakers overwhelmingly use u, not na, so Večeras ću povesti djecu u park is the natural choice.