I am all about creating lots with sims that sole purpose is to populate my game. If it was me, I would create a residential lot with one adult and 7 toddlers. I would decorate the lot just like I would a public toddler lot (toys, jungle gym, etc. You don't need beds or a kitchen because you'll never be playing this lot, but maybe a grill and a bathroom would be convenient). I would have my Sim go to this lot with the 1 adult and 7 toddlers and hang out until they meet each one and then play together with the stuff on the lot. Then you know at least 7 toddlers and can have one heck of a play date at your Sim's house.
