Hey RichieSSZ28,
It still sounds like using the Ask to Buy feature may be the best option in this scenario. Here’s how:
1. Open the Settings app.
2. Tap your name.
3. Tap Family Sharing.
4. Tap Ask to Buy.
5. Tap your family member's name.
6. Use the toggle to turn on or turn off Ask to Buy.
Approve what kids buy with Ask to Buy - Apple Support
Combine that with the steps in here to prevent in-app purchases using Screen Time:
1. Go to Settings > Screen Time, then tap Turn on Screen Time. If you already had Screen Time turned on, skip to step 3.
2. Tap Continue, then choose "This is My [device]" or "This is My Child's [device]."
• If you're the parent or guardian of your device and want to prevent another family member from changing your settings, tap Use Screen Time Passcode to create a passcode, then re-enter the passcode to confirm. In iOS 13.4 and later, after you confirm your passcode you'll be asked to enter your Apple ID and password. This can be used to reset your Screen Time passcode if you forget it.
• If you're setting up Screen Time on your child's device, follow the prompts until you get to Parent Passcode and enter a passcode. Re-enter the passcode to confirm. In iOS 13.4 and later, after you confirm your passcode you'll be asked to enter your Apple ID and password. This can be used to reset your Screen Time passcode if you forget it.
3. Tap Content & Privacy Restrictions. If asked, enter your passcode, then turn on Content & Privacy.
4. Tap iTunes & App Store Purchases.
5. Tap In-app Purchases and set to Don't Allow.
Prevent in-app purchases from the App Store
Take care.