I've lived in the Boulder area for about 15 years now, and have no plans to leave in the near future (although I have been thinking of moving south eventually--it's getting kind of crowded around here). I'm not terribly familiar with Parker or Castle Rock. Pros for me are: lots of people with similar lifestyle ideas; beautiful all the time, everywhere; Longmont (where I am now) has a small-town feel, but also four or five Indian restaurants and at least 3 yoga studios, with easy access to Denver for "big city" activities; lots of outdoor and family stuff to do. Cons would be: expensive to live (and costs are high in proportion to wages); sometimes I get annoyed by what I perceive as a level of smugness here that I haven't notice living elsewhere (but that doesn't mean it wasn't there); lack of cultural diversity outside of some parts of Denver. For your family, there is also the consideration that there are lots of chiropracters already established here. The job market is very soft right now, and people aren't spending money the way they used to. Frankly, you may not be able to survive on one income here until your DH gets established.
I would advise that you do some more research, check online for housing prices to see if it's affordable for you, and have your DH see if there are local chiropractic professional groups who can give him information and advice. He might need to join a more established practice to start with, or connect with other healing arts folks to share office space and clients (massage, maybe a naturopath or nutritionist, herbalist).
The conservative/right wing thing is less prominent around Denver than in Colorado Springs or the Western Slope, by the way, but it's still around.
There is also the point of view that you could connect with other, like-minded families in the IL area and create more support for "our" way of living there. There are probably more people like "us" there than you relaize, but there may not be a good way set up for them to meet each other. OR you could stay there while you accumulate some savings and your DH acquires experience, then move here with a financial cushion and some experience in running a practice.