It sounds like your first metric was a really good ride, and for a worthy cause too. The charity rides go better when the event is well organized. And having that much elevation gain on your first metric is exceptional.

It does help to ride with cyclists who are at your own pace approximately. I know the advice is to bike with groups that are faster than us, but c'mon, in our 50s, just how much faster are we going to get? Where we can get better is in strength, power and cardio endurance, and them sometimes we get a really good ride, like when the wind isn't blowing hard and we are well rested, and we can fly at speeds over 18 mph for miles and miles, but mostly the average speed just goes up in tiny increments or stalls out completely. So stick with your cycling friends, ride solo when they are not available, and get out on your bike and keep on enjoying the miles.

Oh I can think of one thing for you to expect on your charity rides next year, and that is that you may start out with your friends at the beginning of the ride, but more rides than not, everyone disappears, and you might see a friend at a rest stop or maybe not. There are always cyclists at the side of the road peering back down the road, wondering where their friends are, but I just keep on going and don't waste time thinking that someone might be behind me. Sometimes I even end up with a slightly faster average speed on many of the rides, even if I come in after my cycling friends, because I may have spent more time in the Porta Potties than they did, but we are usually within a .5 mph average of each other, even if we end at different times.