Hello Martin (and Michael).
Tangentially related, there’s a discussion on adaptive athletes that might have some useful ideas: Amputee, Disability, Under 1 w/kg group rides out there?
There are group rides that have “rubber-banding” enabled to keep people of differing power levels together - that might be an idea.
Further, there are secondary apps that can be used to alter the data for people like kids and adaptive athletes, to allow them to keep up. They’re discussed in that thread, and here’s a direct link: https://www.patreon.com/posts/ftp-to-boost-or-43281802