I wear skirts (regular slightly above knee length) skirts over my cycling shorts (lycra) when I am riding many miles in traffic, doing errands, etc. Or I wear regular shorts.

I would highly recommend that you wear nicely fitting lycra shorts with a chamois on any rides you do over 40 or 50 miles. If you do enough group rides during your training phase you will see enough lycra on enough body types to de-sensitize. Riding for many miles, the comfort of a good lycra short can't be beat.

The last group ride I did I only had my short lycra shorts with me. Somewhat embarrassing when I thought about it, but I wanted comfort during the ride. At the end of the ride, I got off my bike and pulled on a skirt over my shorts. No biggie.