LOL, it's not a bad size for a terrace. The dining room is kind of the pet room.
We have 4 gerbils, 2 mice, 2 dogs and 4 fish tanks (had 10 at one time -waaaayyy to much work) and at the moment a pidgeon the kids next door rescued from some other kids that were using it as a football - it's made a full recovery but is too young to fly yet.
Your 5yo would love gerbils, mine does! We're getting rats again next