I would two RSForm!Pro rules to validate that the date of birth entered (using the Birthday field).
The "Child dob" rule is valid if the date of birth results in an age between 4 years and 11 years on 31st August for the current year.
The "Leader dob" rule is valid if the date of birth results in an age of 12 or over on 31st August for the current year.
You obviously have to have RSForm!Pro to complete this project. I am expecting you to provide an update for the [url removed, login to view] file.
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