Hi, I've been through all this with my nearly 17 y.o.; she had meningitis as an infant and struggles through school academically and socially. I'm a teacher too, so I'll give you a link to my site of educational websites.
I would hire a tutor to work with your child from now on. Once you get into middle/high school, you'll need a few who specialize in math, science. It's so worth the $. The school IEP will help, but nothing can replace the extra benefits of tutoring, the confidence he'll gain from it, and your peace of mind not having to watch him struggle through his homework. I would also continue to work with him throughout the summer, just a few minutes a day, to keep his skills fresh, in math and reading. www.rocketlaunchers.org/launchpad.html (go to math and reading). For reading, I would highly recommend also getting a book AND a cd book (or playaway, ask librarian) so he can read-a-long and see the words.
Socially, have a Boy's Night Out once or twice a month for a few years. I did this with my daughter. Invite a few kids from his class for a few hours: popcorn and a movie, flashlight tag, simple and inexpensive activities. You may find parents reciprocating after a while.