The problem of dad not wanting to put the kids to bed (in the case of your example) is still there, whether or not the parents are open and honest about it. So

The problem of dad not wanting to put the kids to bed (in the case of your example) is still there, whether or not the parents are open and honest about it. So what you're really asking is "How do you balance honesty and protecting childrens' feelings?" Which is not a flaw of a bidding system, at least not more so than any other system where you actually talk about what you want.