Travel Note
The meet-up, brunch and reception will all be in Denver. The meet-up/brunch will be at an AirBnb some of John's family will be staying at in the Villa Park neighborhood. The reception (Grow-N-Gather) is in the Englewood neighborhood near University of Denver. The actual wedding ceremony is approximately 30 minutes away in Eldorado Canyon State Park, near Boulder. It is recommended to carpool, as often as you're able. If you book an AirBnb in the heart of Denver, all Denver-centric activities are an easy Uber-ride away. But there are many wonderful rentals outside the city if you're looking for something with a view.
Flight
Flying into DIA is easy. United, Delta & Southwest Airlines fly non-stop into Denver. Once you land, you can rent a car or take an Uber/Lyft/taxi $30-45 in approx. 30 min. There is the A-Line train that will take you into Union Station (downtown Denver) for $10/person in 38 min.
Train
John has used this to the airport and it is very convenient, clean, safe and cheap!