Maxtech,
At peril of teaching granny to suck eggs, have you contacted your local PFA struts. We do a lot of Young Aviator flights. Similar format 20 to 30 mins airbourne and we issue a certificate to the kids as a momento of the day.
Have a look here for contact details
PFA Strut listing
And here for .
Young Eagles which is what the scheme was called up until recent events ment we had to change to Young Aviators.
I'm afraid that due to some peckish bovines I can't help you myself, but best of luck on the day.