Discover University Challenge Ideas

I'm doing a single mom lets play myself. However I'm not so sure what rules to set for myself. I think it's a bit too easy that in the some the babies and toddlers just go to daycare whenever your sim leaves the lot for free. I was thinking of making a rule for myself that if the m wants to leave the house for anything else than lectures, she should pay $20 an hour daycare fee or something. But I'm really open to any other ideas to make the gameplay a bit more interesting for me :)