My advice is to book way ahead! I always lay out our Yosemite plans (we go every year) in January so that I can be ready for the first round of camping reservations that are released in Mid January. I am sorry I have not hotel recommendations as we only camp, but my parents like the Yosemite Lodge because it is a real hotel (not cabins or tents) but it is a lot cheaper than the Wawona or the Ahwanee.
May (as someone else noted) is excellent! The falls will be full of water and everything will be green! I also recommend a bike ride in the valley and if you are up in Mariposa my two most favorite hikes are Sentinel Dome and Taft Point. They are two short hikes with amazing views of the valley.
Have a great time!
