This is coming from an AF brat, but I'd say, from a dependents POV, Nellis and Travis are pretty nice.
Travis- David Grant and the base in general is huge, and it has great amenities, given its size and mission. Vacaville/Fairfield are decent areas, and you have the Bay Area about 40mins to the west, and Sacramento 40mins to the east. Napa Valley is like 30mins to the north, and the weather is awesome.
Nellis- Vegas. What thoughts are conjured up in your mind are totally individual when that name is brought up, but it really is a decent place. My parents are actually stationed there currently, so I have quite a bit of experience with Nellis. Like Travis, its a gigantic base with many,many missions. O'Callahan is pretty big, it may have about 50 beds (?), but I may be mistaken. I do know they have a VA associated with it. Anyhow, on to things I do really know... the BX is redone, and it's the largest in the AF supposedly. The commissary isnt too bad, but honestly, shop offbase for food. As with Travis, the services are pretty good- the NCOclub leaves a bit to be desired, as does the OC. Housing can be tough to get, but they were remodeling, and adding new quarters, so things may be different. If you choose offbase housing, do yourself a favor and take something a bit of a drive from the base. The north side of LV/city of N LV outside the base are not a good places to be, so make a 10-15 minute drive into work, and get a nice house, rental more in the city.
Feel free to PM me if you have questions about this or anything else re: Nellis. Overall, you'd enjoy Travis and Nellis, and probably CO Springs, but I left CO when I was 7, so I cant really remember much about that. Hope this is helpful, and like I said, its from the dependents perspective. Best of luck