A cheesecake is not really going to be primal, between the sweetness and the dairy. There are ways to fake it I suppose, and ways to make it "more primal" than a standard cheesecake... but doesn't that just teach them that healthy eating = eating passable approximations of what they really want?
Looks like you may have two potentially-opposing goals here:
1) have a treat for your birthday (20%)
2) give the kids a teaching experience about healthy, delicious primal food.
You might be better served pursuing those two goals as separate exercises, since cheesecake doesn't strike me as a great working example of healthy primal food.
But hey, maybe there's some non-sugary, non-cheesy cheesecake recipe out there? (I can't imagine calling it "cheesecake" though...)