John,
Different groups rally differently, but I can tell you what you might expect at the YNP rally.
RV Forum rallies emphasize integrating new folks in with longer term members, and sometimes longer term members have not been to a Forum rally, if that makes sense.
In my case, for this rally, the emphasis will be on getting folks the most information and experience in the short week everyone has to enjoy this vast (3,000,000 acre) national treasure.
There will be folks who gravitate towards hiking, some for touring, some for photography, some to just see what they can see. There will be some group get togethers, at least one group dinner, possibly a pot luck, and who know what other surprises.
While there will be some structure to make sure folks can enjoy this rally in groups, you are not REQUIRED to do anything you don't want. Typically there is a happy hour where folks interact, tell their story of the day, and connect with others they missed that day. Happy hour can be hit or miss because folks are out having fun, so we will have to see how that works in YNP where the daylight will seem to go on forever.
The rally actually takes own its own course as folks suggest things, group up, and then decide how they want to enjoy their day.
I think you will find that showing up is your first and only obligation, and after that, you will find a pace with folks you'll like.
You should not let the snow fool you, because that should be isolated to some of the upper elevations at that time, there may be a road closure or two in the park, but the difference at that time of the year will be the amount of people in the park itself. Single lane roads don't lend themselves to the bee-jillion tourists who come when school gets out, and that will be in your favor for crossing the park at the maximum 45 mph speed limit.
Stay with this thread and decide for yourself if these are the kind of people you want to spend some time with. The majority of the folks we travel with over the year we meet at an RV Forum rally.
We hope you can make it!
Kim