I have these, but we don't find too much time for them. We keep DS' workbooks in the car, mostly.

When he was five, he went over to his cousin's house for a few hours on a Saturday. The cousins were 11 and 15. They had an old Brain Quest Questions and Answers cube for third grade and were playing with him together on it.

You should have seen his aunt's face when we went to pick him up....

Priceless.

(As a woman of few words, she actually put together a few paragraphs for me. LoL)