I have thoughts on this topic and I can say that I don't do a lot of group rides because of your (initial poster's) fears.

Most LBS or organized group rides called "Beginner Pace" or "Social Pace" or "Leisure Ride" are truly NOT for beginners. Most rides are geared 14-16 mph average, which is not the pace most beginners ride (at least the ones I know). Often, but not always, the distance is 20-30 miles! Now come on! That is NOT a distance that beginners can ride.

Also, if you are new and fearful, I do NOT recommend that you try to "draft" off another cyclist. That skill needs to be developed and not something I would recommend for a first time rider. If you want to learn that you can do it alone with your husband and practice before doing it in a group.
I think that people who cycle a lot or who have been doing it for years forget what it's like to really be a beginner. Experienced riders often take for granted seemingly little tiny things that might be a HUGE deal to a newby.

So....go on the group ride with the goal to just show up and finish. Anything you achieve, this first ride, beyond that is gravy. Have fun and please let us know how it goes.