Jackie I took a 14 day Family tour with my 11 yr old. There were in fact 14 children on our tour.. our tour group was 26 people.
Kids ranged in age from 8 to 17. Eleven of the children ranged from 11 -16. ( we had one 8 yr old, one 10 yr old , and one 17 year old, the rest were 11 -16.
We met up with another RS tour group at a rest stop. They had two teens in their group.. both looked over 16 or 17. The rest of the group appeared mature ( over 35 or so )
I think your kids would have fun on either type of tour.. but I do think they would enjoy the Family tour more.
There are some slight differences ,, in many places you get private local guides.. the one for the Louvre actually worked for Paris Walks .. a local company and specializes in Family tours and making the Louvre interesting to children.. I had been to the Louvre on my own at least 7 or 8 times before I took this tour and I thought the tour might bore me a bit.. but this guide pointed out some trivia and interesting facts that I didn't know about even.. ( and when I was 13 I was given a private all day guided tour of the Louvre by my grandmother.. which was the start of my love of loving museums.. !)
As I said .. any RS is going to be fun,, but I do think the Family tours add a little something .. plus the kids on our tour were all so awesome.. we had no issues at all .. the kids seemed to all love being on this adventure together.. kids of different ages mixed easily, and even within the group kids got to learn about what it was like to live in different areas of the United States and Canada.. ( my dd had no idea kids in some States went to school in shifts.. and started at 7 am.. !)
I think points other bring up are good.. the type of tour you take and time of year may influence group make up. ''
I am surprised that RS did not give you an idea of group make up though.. I phoned and asked,, I did not want to book a tour with only older teens on it .. or only boys.. I wanted to be sure it was a mixed group at least. They did tell me that most kids signed up were between 10-16 and they were right..
PS we had one single adult on our trip. A young man( 22-23 ish ) .. his parents had given him the trip for a graduation gift of some type and for his dates this was the only tour they could get him on.. so there he was stuck with families.. and he had a GREAT time.. everyone adopted him.. the kids liked him, the adults liked him, and he shared a room with the assistant guide who was maybe 25-26 anyways. So my point is.. the tours are fun for everyone even if you are on a tour that may not contain the exact demographic you are looking for..( I still think if the destinations appeal I would choose the Family Tour though,, but if really interested in another area then go for it)