Will the 3 locations mentioned in the descriptions be the only places we can build? And I guess the pets the kids can have will just be dogs?

unless you want skeevers ,a cow or mammuth or a giant as a pet yup only dogs and its good already , ohh unless you want a khajiit in the house im mean at least is a cat right?

Probably if they had more then 3 locations they'd mention them. The real issue is Skyrim's map is largely occupied so usable realistate isn't that abundent.

if it was just dogs I'd think they'd have said dogs. So I presume other pets may be available.

I honestly hope we're able to marry more people. This DLC will be nearly untouched if I can't get myself a khajiit wife.

Would a Khajiit require a litter box?