HS can be better for preschoolers (Ariel, B&B show, Disney Playhouse show, character greetings, Jedi Training etc..) but for a 12 month old I would still do Epcot because like others said, the World Showcase is so nice to stroll around in and at that age, she won't care too much.
If she is walking/crawling, you can try the exit area in Mission Space which has an indoor play area. The older kids go up high but there is a same level smaller area that kids can crawl thru (think Toddler area of Chik-Fil-A) with some mirrors too. That is a nice break from the heat. You and your DH can kid swap for Mission Space too.
ImageWorks is in the exit ride of Journey into the Imagination (which she can go on, just cover her ears during the loud parts) and that is fun for crawlers/walkers too. She will love the water fountains by the entrance too.
She can go on Spaceship Earth too.
In World Showcase, she can do the boat ride in Mexico, Frozen Ever After, play with the toys at multiple countries toy stores, see some street performers and characters.