As a homeschooling mama I know that what works for one child may not work for another. But I've found a math curriculum that both kids have been thoroughly enjoying.
Life of Fred books is a ten book series starting with Kindergarten and working up to fourth grade material. There are also other series that go up through the high school level. Instead of being a text book, this is a fun story about Fred, a 5 year old prodigy math genius. Throughout the hilarious stories, Fred encounters situations that require solving math problems. These stories are entertaining and so weird that the kids love listening to them! Even Becca will sit down for the younger books to listen to the stories.
The books make learning fun. For example, in the first book, APPLES, which is geared towards Kindergarten, you will learn telling time, days of the week, colors of the rainbow, and more.
While I would not use these solely as a math curriculum (and I don't think they are intended as one) we do read a chapter a day after we finish our own math text books/work sheets. Each book lasts us about a month (usually about 18 chapters per book). At the end of each chapter are some questions that reiterate what was just read about.
I see that they now have Life of Fred readers that I think Joe would love. I may have to include those in my next order!
I've found Educents to have the best price on these books. You can earn "Educent Bucks" for future purchases as well and if you sign up through this link you will get $10 off your first order of $25 or more (on anything on their site, not just these books)!
Referral links included in post.