Been to The Hall several times. Everything, the museum, grounds, and ballpark are very compact and easy to navigate. Finding a parking place is easiest if you go there the night before and stay in a local hotel (Holiday Inn Express recommended). My advice is to drive into Cooperstown an hour or so before The Hall opens, especially in summer. You should be able to find street parking within 5-8 blocks of The Hall. I think that the HI has a shuttle service in, but we did not use that. Bottom line is that driving even very early from the City to Cooperstown will not allow sufficient time to do The Hall justice. They close early, too.
Once inside The Hall, either stick together if you want to be with one or more in your group or fan apart and see everything at once. Keep note of what you see "special" such that you can bring others back around who might have interest. Things are very close together and quick to re-find. If they are conducting a special exhibition at a time when you are there, by all means GO. It is often showcasing a specific piece in the collection that has never been or is not unusually shown to the public/. There will always be a learned HoF guide to explain and expound and, if you are REALLY lucky, a HoF might be on hand.
As for meeting, I’d just pick a time and tell everyone to meet in the gift shop, which is large and varied. That way, if people straggle along, the others will have plenty to look at it nt interim.
Have a great time and, if you are a die hard baseball fan like me, bring an extra box of tissues along with plenty of memory card capacity.