I just re-read my own reply. I mixed up the advice in my first 3 words of the advice part. Must have been multi-tasking. Sorry.
Correcting, and clarifying:
Borrow money from them. Post a daily rate that changes, based on their interest in lending you money, but lock it in once the deal is struck for a specific term.
Do it in BTC terms. High interest rates. I'm talking like 200%.
Kids need to see and measure the difference day to day. From their horizon, any fiat is stable.
Presumably you could afford to pay triple digit annual interest for a week or two on on their (assuming small) stack.