They would have fun in Santa Fe. There are many meeting capable hotels with good facilities. It can be warm, but usually all that bad there due to the setting and altitude.
I'd also look at Jackson Hole. The Jackson airport has good connections to several hubs.
Denver is good, but if you are headed there, go just a few miles further and meet in Boulder.
Thinking Utah? Fly into Salt Lake and then drive up to Park City.
Be aware that a meeting in the middle *isn't* a compromise. It inconveniences both sides as everybody has to travel. It is simply mutually inconvenient. If everybody has to travel anyway, then feel free to pick a good place (like Seattle or Vancouver... BC, not WA) and have a good meeting. Adding a couple hours to half the population is better than adding 6 hours to a group that doesn't have to go far.