Heather, it's OK to say you can only deal with focusing on one (or 2) thing at a time. That doesn't make you a terrible parent or that you are not meeting his needs.
That is a LOT of therapy for a school aged. A LOT. Just speaking from my DD's experience there is not way she or we (as parents) could have managed all of that at one time. Therapy involves work outside of the therapy session as well in order to be successful. I would consider carefully how much you think you and your DH can truly commit to doing with your DS this year.
Most people we know focus on 1-2 therapies a year. And you can always start with 1 or 2 and then add in more if you feel like he needs more.
Beth, mom to older DD (8/01) and younger DD (10/06) and always missing Leah (4/22 - 5/1/05)