Feel like Breck, Keystone, Vail and A-Basin have the best Spring Break scene. Been my experience at least.
Party-wise, probably Breck and make a plan to go to A-Basin for a warm, sunny bluebird weekend day. A can't miss. Wear a costume. Bring a suitcase of beer. Act the fool.
Do you want a formal campground or just a spot to park a camper or pitch a tent? National forest is free camping and probably your best bet as most campgrounds are dry at that point (if even open). Plenty of spots all over Summit and Eagle county for that.
Hiking is going to be a challenge. Mostly everything over 8000 feet is going to be socked in so you either gear up or you hit some lower elevation trails on the front-range or some places in Buena Vista or maybe out towards Eagle/Glenwood that melt out earlier, but in April you would have to do a little research as some may still be socked in.
