I don't do group rides so I can't advise you about the ride. But I recently rode in a very hilly part of south central Wisconsin. Here are the stats: 3700 ft of ascent / in total 68 miles.
I calculated the hardest climb to be about 8% when my heart rate was 175.
The TdF would classify that as an Hors Category climb. (No bar room jokes please.)
OK... so I'm not going to France...here's the rub:
I climbed 249 ft over 3168 ft distance (0.6 miles).
The typical TdF Hors Category climb is 5000 ft in 11.8 miles!!!
And...they do it fast:
/"One last note. I think it is inappropriate to compare the ascents of
climbs by the European pros with the efforts of us mere mortals.
I have said this time and time again and I will repeat it now. It
is very, very hard for the average person to comprehend just how
fast the pros climb the big passes. Pace makes all the difference.
Riding a climb is very different than racing it."/
So really, if your club ride is geared toward folks like yourself, who are relatively new to cycling, then it should be no problem. OTOH, if it is intended for TdF wannabe's, then you will be dropped and you will spend the time riding be yourself.