@HarryPottersMum my DD goes to the main kids club usually with no problem. I think Neilson holidays suit her because it's quite structured compared with other types of holiday. The kids club times are set times each day (although vary across the week) and each club prepares a daily planner which is usually left at the meeting place the night before. So we can look through the day, identify any issues then and discuss what times she'll be in / wants to avoid etc. We always try to encourage in club as much as possible (cos we need a break as well!) but understand she may not want to be in all the time.
I can't remember if Stingrays can sign themselves out or not - the younger Sharksters cant but the older Surfsquad can. DD was happier once she was allowed to sign out herself although it meant we were a bit more restricted with heading out on activities. 10 seems a bit young for that but it's worth checking.
They do loads of water based activities, lots of time in the pool swimming but also pool quizzes and games, take them sailing, kayaking, playing on the paddle boards, play tennis, sometimes watch films at lunchtime to keep out of the sun, Zumba, treasure hunt type activities around the site. Most evenings they can join the kids club again for dinner and social/movie or stick with you. Outside of kids club they can try waterskiing or wake boarding a couple of times in the week which DD loves. All our DC have had a brilliant time in the various kids clubs, our eldest is now 17 and upset that this will be the last year. We've found the staff to be excellent at including everyone. All kids get a rash top - different colour for each club, so they can be identified with their group. Stingrays is red I think?
The food arrangements at Neilson are also really good for DD, lots of options at each meal, with the same basics always there so she doesn't have to be adventurous if she doesn't want to be (toast, cereal, fruit, eggs, beans etc at breakfast, pasta, toasties, chips at lunch etc) but lots of varied local food for the rest of us.
Before we go on any holiday we look at the hotel online, talk about what the sleeping arrangements might be so DD knows what to expect. At Lemnos we stayed in the hotel itself with rooms right at the back and away from the pool, it was very quiet and out of the way. Friends stayed in the garden rooms closer to the pool, much nicer outlook but noisier with people wandering past between the beach/pool and restaurant.
This is really long now, I hope that helps, feel free to PM me if you have other questions.