Yellowstone 4th of July

It's likely to all be busy (though not to say you don't have a chance for a site.) If you've got reservations for that whole time at FB, you can probably get it changed, just take the nights out that you want to camp in/near Cody, and return. Not sure that's how they'll want to handle it - they may insist you cancel and try to rebook (which could leave you w/o a campsite in the park at all) - but it might be worth inquiring. Depending on the size of your TT, you may find precious few sites in the nonreservable (and smaller) CGs that you fit in. Something to keep in mind.

We are also going to visit with old friends in Cody so this is only a change in WHEN we go to Cody. We have a full month planned in Yellowstone/Grand Teton and Glacier so I'm not worried about letting them pick the activities a few days. I'm a organismal biologist (with an undergrad background in geology) so they have had no choice but to experience the wonders of nature 365 days a year for the past 11 years ;) - sometimes they just want to do "normal" things. Believe me they will be tired of having to listen to Mom's prattling on about trophic cascades and keystone predators or the Yellowstone caldera by that point in the trip and need a break.

That said, would it be any advantage to deal with Fishing Bridge for a single night on Sunday and campground hunt Monday morning or should I just go looking for space in a unreservable campground Sunday afternoon? I have no idea how a holiday weekend will change the campground migration patterns.

You'll be in Yellowstone. Arguably the greatest, most diverse, and most unique national park in the country. Geysers, buffalo, paint pots, canyons, bears and hot springs abound, to name a few. And don't forget Grand Teton and Jackson Hole.

Forget about the fireworks.

check to see if West Yellowstone has any fireworks events going on. It's much closer that the other towns...sits right on the edge of the park.

Have to agree with the rest. This is an excellent teaching opportunity for a number of reasons. First and foremost it's a way to teach them that sometimes you can't always get what you want when you want it and that it's not the end of the world. Also, you have the opportunity to "substitute" something that is spectacular in it's own right that will allow you to showcase the beauty of nature. You can go to fireworks far more often than you will get to Yellowstone.

X3 - Fireworks happen every year on the 4th and in some places on other days. Yellowstone is a unique place on the planet and you're not likely to drive all the way back there to experience the things you missed because of something as commonplace as fireworks.

I'm going to second that. They'll get over missing fireworks and there are way more opportunities to see fireworks than there are Yellowstone unless you are a local.

Schedule another trip for fireworks. I've been in DC, San Diego, and Yellowstone on the 4th of July. DC is a trip to make but even that spectacular fireworks is over in an hour. Watch Ole Faithful and a sunset to celebratet the Fourth.

Fishing Bridge to Cody is a drive and you're making it really difficult. Get your kids ready for life and disappoint them and stay in YNP. If that's too cruel go to the geyser area, give them multi-colored glasses and watch Old Faithful and the other geysers go off.
Of course that's just my opinion and I could be wrong.