Hi Tara,
While both of these dining experiences are truly wonderful, if I were taking a five- and seven-year-old to the Walt Disney World Resort, I would choose the 
Hoop-Dee-Doo Musical Revue at Disney's Fort Wilderness Resort and Campground over the 
Spirit of Aloha Dinner Show at Disney's Polynesian Resort.  Unless your kids are particularly fond of food with a Polynesian flair, I have found that kids are more likely to enjoy the traditional homestyle American dishes (fried chicken, cornbread, and strawberry shortcake) at the Hoop-Dee-Doo.  (Of course, Disney does their best to accommodate kids with a selective appetite at the Spirit of Aloha Dinner show with a limited children's menu).
With regard to entertainment, I have also noticed that kids seem to love the slap-stick comedy and corny jokes at the Hoop-Dee-Doo.  My son attended this dining experience with his grandparents when he was five-years-old and he still talks about it today.  It was a wonderful night out and it seemed perfectly appropriate for a child his age.  
Therefore my vote is for the Hoop-Dee-Doo.  Yee-haa!
Jill