i went on a Medditeranean cruise for my 10th birthday the last week of septemeber. being that i was ten i wasnt exactly looking for teens. and since school was already underway and not many people took their kids out of school during the 3rd week or so, there were basically zero kids.
but many people tell me that medditeranean cruises in the summer are a big hit for familes and kids/teens of all ages.
medditeranean cruises are super fun! because you get to see europe without having to stay in foreign hotels. and you get to experience many more places then you would on a week land vacation in europe.
hope this helped and ENJOY!