I teach 4th grade and we will be doing Everyday Math for the first time in August. Sounds like fun.
Basic facts practice is always good for 4th grade so maybe work on some times tables, or add/subtract 2 and 3 digit numbers. I'm not sure if 3rd grade to division in Everyday Math or not, but I would guess they probably do related division facts for multiplication problems.
Here are some good websites you could use that are on my classroom site...