One fun idea I just had could be that a family has a special tradition just before heartswarming. The kids will get most of their presents no matter what (naughtiness is dealt with with spankings, groundings and other things right away) but the parents always hold back 1 thing they really want. To get that one the kids have to make a list of every naughty thing they did that year. If the parent approves they will give them an appropriate spanking. The kids don't have to do this but the present will just not be bought in that case.

7505583 What's stopping kids from withholding some of the bad stuff they did?

And if there is a goody-goody filly, she'd have no choice but to make up bad things in order to get what she deserves (and by that I don't mean spanking but the present she really wants).

7505588
1: Maybe that would encourage her to be naughty a little more often. Children never getting in trouble is not healthy as they should push borders and themselves.
2: Such children are exceedingly rare.
3: The parents still decide how much so it can just be a soft 5 token spanks