I'm doing 100 baby challenge, but I haven't finished it yet. I really like it. The fathers of the children are all Maxis premades and/or other Maxis Sims that I've downloaded in that save. It's fun to see how the kids will look like when they grow up.
I've tried legacy challenge, but I didn't like it because there were too many rules that I kept forgetting. Also the rule that I would've had to build the family house by myself (according to the rules I wasn't allowed to download from gallery) was a no go for me. I can't build anything and I wasn't interested of playing a game with a rich family (the founder did gardening and made huge amount of money with dragonfruits) that live in a shoebox.
I wasn't having fun with it and I decided to ditch the challenge and download the family a nice home from gallery and continue playing it as I wanted, a legacy play without rules.