Gareth,
My two sons are now 26 and 24. The eldest was always interested and was my full time crew from the age of 12, until he got his own Dart 18. He now races a Spitfire. The second was more nervous ("Put it down dad" if I flew a hull)and was 15 before he asked to crew. He crewed for me on a Dart 18 and after that for three years on the Hawk. He is now a senior sailing Instructor.
I don't think that you will have to do any pushing !