I vote for Longmont - reasons:
1. Friendly city
2. Outdoors easily, hiking, biking, walking, skiing close, etc
3. Dog friendly city
4. Housing not too expensive
5. VERY family friendly - we always have parades, etc for events throughout the year
6. WE GET GIGABIT INTERNET!!!! (Sorry to shout, super excited about this coming) - AND for a limited time, if you get it within three months of it being available, it's only $50 a month! Up and down!!
A few other thoughts...
Colorado is very "purple" - that is, politically the spectrum varies and so if you lean one way or the other, you may want to live with those similar to you. Most of the cities mentioned here are in the north (CO Springs being the exception - other places in the south include Pueblo and Castle Rock) and along the "Front Range" (ie, close to I-25) and are more liberal areas. Taxes are nice here, although Boulder county (where Longmont is) has higher taxes for a lot of things - but you do get some benefits of those as well.
I think if you are only planning on a 10 year stay, any of the cities mentioned are good, although I do think your family will enjoy a "smaller" place - once you get over 500k people, it just doesn't feel the same. But the opportunies are bigger in a larger city, and you can always live "near" it (IE, Longmont is about 45 minutes from the "big city" of Denver).
Also consider your wife's job - what are her prospects/plans? What are her skills? Other places to consider are... Raleigh NC, Charleston SC, the DC area in VA, the Austin "area" in TX, Phoenix AZ, Albuquerque NM...
Finally, do you like snow or hot or other weather issues more or less? Here in Longmont, we get pretty hot (100+ a few days, mostly 90sF high in the summer) and pretty cold (we've hit -25+F in the winter with wind chill) but for the most part it is in the 15-90F range most of the year. We also get a lot of sun and the snow melts fairly quickly (full disclosure, Longmont sucks at clearing the roads after snow, they let it melt so the first few days can be hard; also, get a south facing house or risk a snowy lawn all winter).
Good luck!