Hi Jennifer!
Welcome to the Disney Parks Moms Panel! I love this question so much because I love both of these shows oh so much! I actually took my parents on the 'Kristen week-long guided tour of Walt Disney World Resort' in March which including both of these events. Not on the same night, but I've got the memories of both that snack box and those all-you-can-eat ribs fresh on my mind. Ultimately I think this plan is definitely feasible.
Hoop-Dee-Doo Musical Revue clocks in at right under two hours, which puts us at an 8:15 P.M. exit. The actual second-showing of Fantasmic! during your visit will start at 10:30 P.M. Check-in for the
Fantasmic! Dessert & VIP Viewing Experience starts 40 minutes before the show, but can be done all the way until the show starts. This gives you 95 minutes from Hoop's exit to the opening of your dessert party check-in. Or, in total you have 2 hours and 15 minutes between the two shows if you're that person who likes to get there just in the nick of time.
Do be aware of transportation. Hoop-Dee-Doo takes place at Pioneer Hall, which is located in the back part of Disney's Fort Wilderness Resort and Campground. This part of Ft. Wilderness is only accessible by a special bus from the resorts' main bus stop, or by a boat from either Magic Kingdom Park, Disney's Contemporary Resort or Disney's Wilderness Lodge. I do think there is enough time to take a bus from Pioneer Hall to the Fort Wilderness Bus Stop, and to then catch a regular Disney bus to Disney's Hollywood Studios. However, if you get antsy while waiting, there should be taxis near the main bus stop or you can hire a Minnie Van.
I hope this helped, Jennifer, and We'll See You Soon!
~Kristen