I'm a little confused about which CG you will stay at since you mention Bridge Bay, Fishing Bridge and Madison. As previously mentioned, Bridge Bay and Fishing Bridge are not the same CG but are only a few miles apart (about 5 total, if that.) And you do know that only Fishing Bridge has hookups, correct?
Can't help you on Canyon CG, but I have heard thru the g****vine that sites there do tend to be smaller/shorter. Bridge Bay does have a mix of different-size sites.
Colter Bay RV Park is nice & has FHUs. Colter Bay CG is different - no hookups, but apparently still nice. We have driven thru the former but not the latter. I'd definitely choose Colter Bay for the Tetons (my personal preference); Gros Ventre has a big following, but is located at the south end of the park, while Colter Bay is near the north end.
July 4th is a very big night in Cody, its rodeo that night being quite popular, so you will want to book your Cody reservations as far ahead as you can. Good for you for getting on your YNP reservations for next year now, too!