Are you talking about the park--or just the showcase.
If you are going to EPCOT--don't miss the showcase. Food, entertainment, and the kidcot stops--my girls have been going for a bit and they are only 5 and 3 (the 5 year old first went as a babe or a toddler, I don't remember).
If you are bypassing EPCOT all together--it is up to you. I would suspect that you may have parkhopping passes. If that were the case--there is no harm stopping by and checking it out. I'd be concerned with 7 days straight at MK.
MGM has Bear in the big blue house and ariel and Animal Kingdom is just fun with all the wild life.
If it were my trip--we may go light on a park, but on a 7 day trip we would hit them all. My girls have been going since age 11 months and 4 months and they have their own things they like in each park.
While your girls may not be in awe like riding on Winnie the Pooh---I'm of the philosophy that any place is suitable for kids of all ages, just have to know where to look.
They have character meet and greets all over (wayyyyy more than when I was a kid) at EPCOT...so Disney has somewhat figured out a way to make EPCOT tot-friendly.
Enjoy your trip whatever you decide

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