Translation:Young children are waiting at the hotels.
I've never heard of old children, so all children would be young by default, don't you think? :)
In English we do sometimes say "young children". I think of "young children" as referring to children in the early years of elementary school or preschool.
That would have to be a fiatal gyerekek, I think, but there is no a in Duo's sentence in that noun phrase.
Are they in the hotels or near the hotels? What does AT mean here? I thought -nál is the position near, beside the object.
Yes, you're right. It means 'near the hotels'. It's maybe not the best idea to use prepositions with multiple possible meanings.