Hi there!
I absolutely love the mini-golf courses! There are two sites, each with two courses, all 18 holes.
Santa's Winter Summerland is located right by Blizzard Beach- so you can take the same bus you would if you were going to the water parks. One course is themed as if it's Santa's summer vacation, the other themed all snowy. (I think the backstory is that Santa and the elves were having a summer vacation but then got homesick, hence the two versions). I did both courses back-to-back which was a lot of fun- and interesting to see some of the mirror images between the courses!
Fantasia Gardens is located closest to the Swan and Dolphin hotel. You can still take Disney transportation but since the busses don't go hotel-to-hotel, you'll have to transfer from a park or Downtown Disney, and then walk from the Swan and Dolphin. One course is themed to Fantasia (as you can probably guess), the other is supposed to look like a real golf course, but in mini-golf format. (I think). I have done half of the Fantasia course but got rained out so never completed it (but did get a lovely non-expiring rain cheque). I have never done the "fairway" course, so have no idea what it's like!
They are definitely a fun diversion!