Lantanatx, you mentioned that you have a month scheduled in the parks. I don't know if it would work out for you or not, but Gillette, WY will be hosting the "World Fireworks Convention" (Pyrotechnics Guild International) August 8-15. I'm not sure of the dates for the fireworks shows, but I can guarantee they'll be bigger than anything you'll see on July 4. They have their convention here every 2-3 years iirc. We "watch" them from our home 5 miles away. ;)
Just thought I'd mention it, in case the timing would work out better. (Gillette is on I-90, about halfway between the Bighorns and Black Hills.)