Thank you for your question
My name is ***** ***** I shall do my best to help you.
You will have to be very careful since you have no legal right whatsoever to limit their spending.
It could be more sensible to suggest and agree that a substantial part of the inheritance is locked into an account that cannot easily be accessed.
Otherwise I would suggest that you arrange for you all to see a financial advisor and get advice on the way forward.
Please ask if you need further details
You are most welcome - get as much locked away as you can!