Hyatt Place Pena station is very convenient to DEN especially if you are willing to take the train but with a bunch of you, it may not be cost-effective. There is little to do in the area after you wake up. Also, without renting a car, getting to Boulder that late is impossible on public transportation. The Boulder Hyatt Place is nowhere near all the cool things on Pearl Street. It is still a schlep or a bus ride. So if you need to walk around, I suggest downtown at any of the mentioned hotels, enjoy the walk around downtown and the colorful characters, grab coffee and snacks at Whole Foods, and take the train or an Uber/taxi back to the airport. The breakfast at the Grand Hyatt is good, the breakfast at the Hyatt is good, the Pena Hyatt place is not great, and the Boulder Hyatt Place is AWFUL.