I agree with DisneyWishes14.
HS doesn’t have anything much these days for little guys (though that might change soon with Toy Story land). The shows are too long for a little to sit through and the few rides available are too grownup for them. EPCOT would be ok, but again, about half of the rides your little one would not be able to enjoy and much of the World Showcase would be over their head.
I would either just go a second day to MK, which would allow you to take it easy on both park days, or I would go to AK the second day and take advantage of the animal viewing and gorgeous themes. AK is our favorite park for any age, but I think would be the perfect second park option for little ones.
(Bring your stroller though! Loads of walking.)