I thought, I'd jot down a few options which might be useful.
At Role Models we provide an ad hoc and part-time Creative Childcare Service. We have a range of 21-30 yr old actors, sports people, artists, musicians etc on our books, who love looking after children, in and around developing their career. The link tells you more:http://www.rolemodels.me/creative-childcare/
For your eldest in particular, we run a one-to-one Leadership Programme of 8 sessions of 90 mins for 10-14 year olds, focused on encouraging children to understand their character strengths and how they can have a positive impact on those around them. It was developed by the Head of Leadership Institute at Wellington College:http://www.rolemodels.me/events/leadership-programme/
We also run other Life Skills Courses as 4-5 day group courses for 8-12 year olds in the holidays. Our flagship course is a Confidence & Resilience Course in Wimbledon and Chelsea / Pimlico: http://www.rolemodels.me/featuredevent/life-skills-courses/
I hope that's useful.
All the best,
020 3637 7107