Since MNSSP is until midnight I can't see why this would be a problem.
We've been to IOA, twice now, once in June, packed and once in late Sept., the year it opened. Both times we got there at opening, walked at a good pace, not stopping in too many shops. We ate only quick bites at fast food stops. We did stop a few times to rest and take pics, we were not running around the whole park at breakneck speeds. LOL
The first trip, year of opening, it was semi-crowded, longest waits were for Hulk and Spiderman. I think those were about 45 min each. We got those out of the way very early, right after opening. We got on all the major rides, saw a good number of shows and rode most of the minor rides. We were easily done with the park by 4 or 5 in the afternoon. This park seems very large, but it is no where near the size of Epcot or MK. Plus the way it's laid out makes it easy to tour, not a lot of double backing.
The next trip was just my teen and I, during June and the place was wall to wall people. For the biggies, like Hulk and Spiderman the wait was extreme, well over an hour. We started by heading there first, got in line for the Hulk, but do to weather it closed. Headed to Spiderman, waited about an hour. We then changed directions and headed counterclockwise back to Seuss Landing and toured that way, work out well. Crowds tend to move clockwise at this park, since the biggies are that way. We saw a few shows, rode all the biggies, except for Hulk (due to weather) and all the smaller rides. Just before leaving we rode Spiderman once more. I think we were done by 6pm this trip. I know we were back to our hotel before dark.
Another thing you can do at IOA is by one of those vip passes, which allows you to hit the front of the line, for most of the rides. I don't know the cost of this, but it might be worth looking into. Get them early tho, they sell out FAST, by the time we checked on them, on our second trip they were gone.
I've never done this, hitting both places, but with my experiences at IOA, I can't imagine this being a problem. But another factor, of course is who's in your party, i.e. kids, shoppers, older people moving at a slow pace.
Have a great trip!
Pammy