Look into using taller doors than normal for a garage, not camper height, but taller than normal, you may have to increase the height of the structure but what you spend extra now will be gained back when you resale down the road. Also 2nd the idea of a third door off the side or back that you can get your mower or snow blower out without having to open up the front and pull a vehicle out.
When we built our two vehicle garage, it ended up being 30 by 26 I believe, I added the door on the side all the way towards the back, allowing me to get a 3rd vehicle in there, which I never did, but was great to park the mower back there and just drive it out, without having to get the other vehicles out of the garage.