Have you ever thought about asking children to make up multiple choice questions?
Make it meaningful by asking them to include what could be common mistakes
e.g. What is 37 away from 56?
A 21 (because people might subtract smallest digit in each number-does that make sense?)
B 93 (people might make the mistake of adding?)
C29- what mistake might this be?
D 19- remember to include the correct answer