There's nothing more Scrooge-like than ignoring your guests' dietary restrictions. While Santa will surely appreciate the sentiment, he may not be able to eat the cookies and milk you set aside for him. In our modern day, many people have food allergies and restrictions, and Santa could easily be one of them.
So this Christmas, do your research and find out what Santa (as well as the reindeer and your holiday guests) likes to snack on, and bake him something special. Leave a couple of these out with a side of dairy-free milk (he'll probably have had his share of cow's milk by the time he reaches your home) and expect to find an extra present or two under your tree come morning.