Like Laura said; unless there is a complication (and even then it wont be a given), your son should be fine by august. Kids heal quickly and tend to run around like nothing has happened within days.
Have you read any of the info in the disABILITIES-stickies? I doubt it (since it would give you your answer

); so here it goes;
GAC stands for Guest Assistance Card. It's nothing more or less than a card stating an individuals needs while at WDW, so each CM can take note of the needs and act accordingly.
What qualifies people? Unlike some people (most, it sometimes seems on the DIS) think it is not about diagnosis. It is all about needs. For instance, some people can't stay in the sun too long because of the meds they use. They'll get a GAC that will allow then (where possible!!!) to wait in a shaded area when the regular line isn't shaded. It doesn't give them front-of-the-line (nobody gets that except kids on their Make A Wish trip), it simply mitigates their needs. Or parents who use their young childs stroller as a wheelchair. With that type of GAC they will be allowed to take the stroller into lines and theatres where they would normally have to park it outside.
So what is the question to ask? Does your son have medical needs that WDW can reasonably mitigate? Maybe I'm missing something, but I don't think so. Who knows, let's be carefull and state he might not be up to the walking. In cases of mobility and/or stamina problems, WDW advices people to use a wheelchair or
ECV and therefor not issue a GAC. Or who knows, he's still a bit tender in the belly, so can't do the rides with a lapbar that comes in contact with the belly. Well, that is something they can't help with. Of course safety comes first and you wouldn't want him to ride with that bar not in the exact right spot either.
But again; you'll probably be asking yourself why you ever even worried about this when August comes knocking.

for a speedy recovery!!