"Everyone's children participated in the holiday."

Translation: Ĉies infanoj partoprenis la feston.

[denaskulo]

holiday=festo? Ne vere laux mi...

[Robert918848]

Festo can mean a religious holiday, celebration or a party, depending on the context.

[andrewgtreantos]

En la festo = la feston ?

[Robert918848]

Yes, there are two ways of saying it:

Partopreni en la festo.

Partopreni la feston.

[donaldo_zouras]

I couldn't find partopreni in the dictionary, so I looked up the parts...
parto= part
preni=take
partoprenis = took a part?
A funny way to convey participate.

[Oceanotti]

You can find the etymology here.