Bridesmaid Dilemma

I’m planning on getting married next year but I have a lot of girls in the family. I have 5 young family members all expecting to be bridesmaids (I haven’t had the conversation yet). The ages span from 11-15 and I would love to have them as bridesmaids, and if I don’t ask them, there isn’t anyone else in the family left to ask them (while they’re still young anyway, they might have each other). But I have a few really close friends that I would also have liked to have had but I don’t want 7/8 maybe even 9 bridesmaids as I think it’s a bit too much as I’m only having a registry office wedding with under 40 people. I debated asking the adults (that I would have had as bridesmaids) to wear the same colour as each other (different to the junior bridesmaids) just for picture purposes and so they stand out as something other than just a regular guest. Or is that over complicating things? Or should I just say **** it and just have all 7/8 of them (but that’s like 1/3rd of my guests😂) HELP! (P.S. In case you couldn’t tell - major overthinker)