This is possible through parental controls. Hold the crowns on the master account then transfer them in small increments to the account you want to use them on. Obviously if you are controlling it you will have to be disciplined when transferring them, but it could be easier to say no to yourself when you have to log in and purposefully make a transfer rather than clicking just one more pack...then another...but maybe the next is the lucky one so just one more...
I expect we've all given into the temptation to buy just a couple more packs when we'd set a limit in our mind!
