I have a few suggestions;

1. Have items they interact with. Like a phone, or a garden.

2. Add the stock market or a sie business for more money.

3. Be able to take a test for the 18 yr olds, then pick a college they got o according to the test "he 18 yr old" takes. This would mean YOU as the player of the game will take the test for the 18 yr old. Depending on the score, the 18 yr old, or YOU get to pick the college they attend.

4. BE able to influence how the kids grow up. MEaning, if they are on the PC alot, or outside..so on...then that will infulence what they like or their jobs.

5. I love the idea of saving up to buy a house. Have different types of houses, with different layouts.

6. Offer more items like clothing, and house items.
Maybe a new fridge, or oven..or even more house upgrades like more rooms or a bigger kitchen.

7. If you add the buisness, have an option of off site, or at home. If at home they can either pay for the site or pay for more room in the house.

8. More jobs.

9. Be able to pick a job for your person.

10. Be able to design your own patterns for things. Maybe be able to move furniture around.

PLEASE becarefull though! Some of these tread with the border of that OTHER game like this...