They are a big help in raising twins, or when you have babies back to back. The only negative of them is that you will lose the happiness points with not teaching your toddlers those skills.
You can get at the least 1,000 points or more from teaching the toddlers to walk and talk. The skill books are a great help also and if you don't want to buy them you can take the toddlers to the library and they will read them while you read a skill book, killing two birds with one stone aspect, parent and toddler skilling up at the same time and saving on buying skill books.
The toys, peg box and the music one (not going to try to spell it's name
), help to keep the toddlers busy and build skills in logic and music.
Just a tip, for next time your sim is going to have a baby, let her have it at home. It gives a head start on relationship with the mother.
As for controlling them, you learn how but it can be frustrating at times. I use the pause button a lot to make sure that someone is doing what they need to do, or isn't doing something they shouldn't be doing.
I try to stop it at five or six, but in a project story I did I had eight a few times and that was a big overwhelming when I had them all doing something different. Worst was when I had a family of seven and four were witches. Two kept doing love charms; not bad except when one would cast it and another family member was close by. Havoc on the family relationship.