Be prepared for a good hike out to Racetrack. If the birds are flying, it's worth the effort.
I usually hunt 12 or 13. I like 12 since it's in the corner and you only have a neighbor on one side. 11 is by itself over on Gay Lake to the south. Never hunted it, but I've heard a lot of shooting over there on occasion. Either 13 or 14 (can't remember) has a big tree behind it that will be in the way if you swing around for a pass shot. I've never done well on 15, but I know other people have. It's also the shortest walk. The blinds aren't as close as Mudhen or Hunt, probably an actual 200-250 yards, although 12 and 13 are a little closer together. They're all on the west side of the lake. If you hunt 11, 12, or 13 there's a back way in to the lake that's a little shorter, but I don't know how well it's marked.
My decoys are super mags so I don't carry a lot of them. About 18 for a long hike like that. If you have a cart or a buddy I'd defintely take more.
As far as shells, I use #3's for everything and an improved cylinder choke. You're probably gonna hear a thousand theories on shot size and chokes, but that's what works for this white boy.
You got lucky if you drew Racetrack on a weekend. Have fun and kill 'em.
p.s. #13 has a couple of nasty holes underwater in front of the blind, or at least it used to. If you do a face plant into the water first thing in the morning it can make for a long day.