I was in Dayton a couple of weeks ago and did spend a full day at the museum. There is a lot to see. The place is huge, and although there were a lot of people, it was not crowded.
When you get there, immediately go and schedule yourself on a shuttle to the stuff that is over on the AFB. The shuttles fill up quickly.
There's lot's of military historical info there too, and more than just the planes.
You can pretend that you're the President on Air Force One.