EPCOT if you only pick 1, or do a half day at DHS and DS instead of a full day at DS. I have 2yo and 6yo daughters. While they like the shows and Disney Jr., Epcot just has so much more. On all of our trips with at least 1 kid, we've really only spent 1/2 days if any at DHS. We will go to EP multiple days, though.
The movies and shows at EP, especially World Showcase, are fun for all ages. There's a lot more interactive stuff, more characters, and more rides without a height requirement. When we were last at DHS in August, our 2yo spent a lot of time in the stroller because we took our ODD on height restricted rides with rider swap - and for a relatively small park, there's a lot of walking to get places. E.g. our FP were for Tower of Terror, Star Tours, and TSMM. YDD could only go on TSMM and at almost 2, didn't really do anything on the ride.
My kids could easily spend multiple days in EP: rider switch w Soarin, Living with the Land and then a meal at the QS or Garden Grill is a couple of hours, alone. The Seas has Nemo, TUrtle Talk with Crush, and lots of space to see exhibits and lose your kids... Which reminds me, hopefully you won't need it, but EP is a much better park for bad weather, because there's lots to do and see in each pavilion.