Learn Hardcore Russian: Их дети играют среди цветов, а потом собираются пить чай. - Their children play among the flowers and then gather to drink tea.

The preposition среди always requires the genitive case to mean “among” or “in the midst of.” So the plural noun цветы changes to цветов when used with среди.

What’s the difference between среди and между? Both can mean “among” or “between,” right?

Yes, both relate to “between/among,” but:

между is used when you’re talking about distinct, countable items (e.g. between two trees, между двумя деревьями).
среди is for things seen as a group or mass (e.g. among the flowers, among a crowd). Flowers form a scattered “mass,” so среди цветов is natural.

What does а потом mean, and why not just потом or и потом?

потом alone means “later” or “afterwards.”
и потом is simply “and then,” neutral in style.
а потом also means “and then,” but а adds a slight shift or contrast—“first this, and then that.” In narrative it emphasizes the next step.

Why is there a comma before а потом?

In Russian, when two independent clauses are joined by а, you place a comma before it. Here you have:
1) Их дети играют среди цветов,
2) а потом собираются пить чай.

How does собираются + infinitive work?

When собираться is followed by another verb in the infinitive, it means “to be going to” or “to plan to.” So собираются пить чай = “they are going to have tea” / “they plan to have tea.”

Is собираться ever used to mean “to gather” (like people gathering together)? How do you tell the difference?

Yes.

Alone or with a noun (собираться на площади, “to gather in the square”), it means “to assemble” or “to get together.”
With an infinitive (собираются + V-infinitive), it means “intend to” or “be going to.” Context and the presence of the infinitive tell you which meaning.

Why is пить imperfective here instead of the perfective выпить?

Using the imperfective пить focuses on the process or habit of having tea (“to have tea” in a general sense). The perfective выпить would stress completing the action (“to drink it up”), which doesn’t suit a planned, casual tea break.

Why is играют in the present tense, and why plural?

играют is the 3rd person plural present-tense form of играть, matching the plural subject дети (“children”). It indicates they are playing now (or habitually).

What kind of pronoun is их, and why doesn’t it change form?

их is the possessive form of the 3rd person plural pronoun они (“they”), meaning their. Unlike 1st/2nd person possessives (наш, ваш), их is invariable—it stays их for masculine, feminine, neuter, singular, and plural.

Why does чай look like the nominative even though it’s the object of пить?

In Russian, masculine inanimate nouns have identical forms in nominative and accusative singular. So чай in пить чай is actually accusative (direct object) but appears the same as the nominative form.

Could you swap word order to Среди цветов играют их дети, а потом…?

Yes—Russian word order is flexible. Putting среди цветов first shifts emphasis onto the location (“It’s among the flowers that their children are playing…”). The original order is more neutral: focus on the subject (их дети) first.