Solution

39373

First name
Eleanor
School
Soham Village College
Country
Age
11

I have found one solution to this problem.

I started by choosing random numbers to test, but soon decided on a more logical method. I used the ratio of OAPs to children to adults to start with. I then played around with the numbers until until I reached £100 and 100 people.

My solution is:

47 OAPs 50 children 3 adults

£47 £42.50 £10.50