FRTDOG,
To answer your concern, yes, there is and will be a significant difference in the age group on your intended trip. Since we just returned this fall from our RV road trip to Alaska, and were often grouped with one of at least 7 different caravans that were basically going the same way that we were, I can speak with some authority. In your 40's you will be the youngest present by a LONG way most likely. I am mid 50's and I was also the youngest in the campground when the caravans were in. That being said, that isn't necessarily a bad thing. Depending on your type of RV activities you enjoy, you may fit right in and never miss a beat.
Many RVers are extremely flexible folks where socializing is concerned. But as for our style of RVing, a caravan would never work for us. But for different reasons. Most of all because of the "group" mentality of the caravans. Because of the cost and wanting to give you the most bang for your buck, the caravans keep you hopping. Nearly everyday the caravan folks were headed off to somewhere, either on foot, in a bus, or public transportation. Often leaving at the break of dawn and not getting back til after dark.
Some folks really love the regimentation, but it would drive me nuts. I like going slow, picking my spots to see, and coming back and hanging out at the RV each afternoon for cocktail hour. And doing that for 60 days is WAY out of my comfort zone. There are lots of potlucks and group gatherings with everybody in the caravan. Again, I can do a little of that, but I like just enjoying the solitude sometimes.
There was quite a cross section of people in the caravans, and most were 20 - 30 rigs of all different descriptions. Shoot, some of the caravan folks had been on 10+ caravans! So it really depends on what you are looking for, and your style of RVing.