re: Denver/Breckinridge in May-best hikes?

We're in another stormy pattern with more snow coming. It dumped up there last night, will again this weekend, and yet again early-mid next week. It's going to be a pretty active Spring. May and June are the meat of mud season. It's why early-mid June is prime rafting season. Follow the webboards closely before your trip. Expect to be post-holing, getting real muddy, or both depending on your hike. Might need snowshoes and/or mud boots, too early to say. Either way, poles are advised.

ETA: If you're staying in Breck, definitely hit Mohawk Lakes Trail. It's a series of lakes and waterfalls going all the way up into the cirque that the highest lake is nestled in. Depending on trail conditions and your group's condition, you may or may not be able to make it up to the highest lake in the cirque, but it's still a great hike. I've done it multiple times. you can fish for Brook Trout in the Lakes too. Sometimes even catch them by hand (without rock damning, that's illegal) in the outlet streams if you're good.