Kad kampiramo s djecom, uvijek uzmemo dodatni sprej i zatvorimo šator prije mraka.

Yes. Kad and kada both mean when.

• Kad is more common in everyday speech and writing.
• Kada is a little more formal or emphatic.

In this sentence, Kad kampiramo s djecom... is completely natural and idiomatic.

Because Kad kampiramo s djecom is a subordinate clause that comes before the main clause.

So the structure is:

• Kad kampiramo s djecom, = When we camp with children,
• uvijek uzmemo dodatni sprej i zatvorimo šator prije mraka. = main clause

Croatian normally uses a comma after an introductory time clause like this.

Croatian usually does not need subject pronouns unless you want emphasis or contrast.

The ending -amo in kampiramo already tells you the subject is we.

So:

• kampiramo = we camp
• mi kampiramo = we camp with extra emphasis, like we as opposed to someone else

In this sentence, the plain verb is enough.

Djecom is in the instrumental case.

The preposition s meaning with usually takes the instrumental:

• s djecom = with children
• s prijateljem = with a friend
• s roditeljima = with parents

The base form is djeca = children, but after s it becomes djecom.

Because djeca is a collective noun with somewhat irregular forms.

Its basic case pattern is not as straightforward as many other nouns. Some useful forms are:

• djeca = nominative plural / basic form
• djece = genitive
• djeci = dative/locative
• djecu = accusative
• djecom = instrumental

So s djecom must simply be learned as the correct instrumental form of djeca.

This is a very important aspect question.

• uzmemo is from the perfective verb uzeti = to take
• zatvorimo is from the perfective verb zatvoriti = to close
• uzimamo and zatvaramo would be imperfective

In a sentence about repeated situations, Croatian often uses perfective present forms to express actions seen as complete each time the situation happens.

So this sentence means something like:

• Whenever we camp with children, we make sure to take an extra spray
• and close the tent before dark

The perfective forms focus on the completed result of those actions.

If you said uzimamo and zatvaramo, it would sound more like you are describing the process or a general ongoing habit, not the completed steps in each instance. In many contexts that version is also possible, but uzmemo / zatvorimo is very natural here.

Because the verbs describe different kinds of actions.

• kampirati = to camp is an activity, something ongoing
• uzeti = to take is a single completed action
• zatvoriti = to close is also a single completed action

So the sentence mixes aspects naturally:

• Kad kampiramo... = while/whenever we are camping
• uvijek uzmemo... i zatvorimo... = we always do these completed actions

This combination is very common in Croatian.

Uvijek means always.

It shows that the main-clause actions are habitual:

• uvijek uzmemo = we always take
• uvijek ... zatvorimo = we always ... close

It does not mean a single event. It means this is their regular practice whenever that situation occurs.

It is in the accusative case because it is the direct object of uzmemo.

However, both words look the same as the nominative because:

• sprej is a masculine inanimate noun
• masculine inanimate nouns usually have accusative = nominative
• the adjective agrees with it, so dodatni also stays the same

So:

• nominative: dodatni sprej
• accusative: dodatni sprej

Same form, different function.

Yes. Sprej is a normal Croatian word, borrowed from English spray and adapted to Croatian spelling.

It behaves like a regular masculine noun:

• sprej
• spreja
• spreju
• sprejem

So dodatni sprej is completely natural Croatian.

Šator is in the accusative case because it is the direct object of zatvorimo.

Like sprej, it is masculine inanimate, so the accusative looks the same as the nominative:

• nominative: šator
• accusative: šator

So:

• zatvorimo šator = we close the tent

Because the preposition prije means before and takes the genitive case.

So:

• mrak = darkness / dark
• prije mraka = before dark

This is a very common pattern:

• prije večere = before dinner
• prije puta = before the trip
• prije kiše = before the rain

Yes. Both are possible, but they are slightly different in style.

• prije mraka = before dark
  Shorter and very natural.
• prije nego padne mrak = before it gets dark / before night falls
  More explicit and a bit longer.

In your sentence, prije mraka is simpler and very idiomatic.

Both can be understood, but kampirati is the standard Croatian verb.

• kampirati → kampiramo
• kampovati / kampovati-type forms are more associated with Serbian or regional usage

For standard Croatian, kampiramo is the better choice.

Yes. Croatian word order is flexible, although some versions sound more natural than others.

The given sentence is very natural:

• Kad kampiramo s djecom, uvijek uzmemo dodatni sprej i zatvorimo šator prije mraka.

You could also hear:

• Kad kampiramo s djecom, dodatni sprej uvijek uzmemo i zatvorimo šator prije mraka.
• Uvijek uzmemo dodatni sprej i zatvorimo šator prije mraka kad kampiramo s djecom.

But the original order is clear, neutral, and probably the best one for a learner to model.

Because Croatian does not have articles.

So where English says:

• with the children
• an extra spray
• the tent
• before the dark

Croatian simply uses the noun and case endings:

• s djecom
• dodatni sprej
• šator
• prije mraka

Croatian expresses meaning through case, context, and word choice instead of articles.