Actual photo from last night's dinner. Note grumpy baby in the background!
When we serve baked potatoes (which we do a lot because, hey, they're cheap!) I chop up the potatoes after they're baked and put them on a platter. I then top them and serve.
This lets everyone get as much as they want without waste. Plus, by topping them ahead of time, it curbs the children that consider butter and sour cream to be the main dish! Leftovers heat up great, too.