Don't confuse Beaches N Cream with regular restaurants. If you wanted to eat somehwere where a waiter or waitress served you then you would want to allow extra time. Beaches is a small establishment that serves burgers and ice cream. The longest wait time you will have there is if you have to wait for a table since the place is small. The meal itself will not take you long.
I understand that at times the wait could be quite long. You may want to have a backup plan in place just in case. There are many restaurants in the area (Epcot resort area). You can walk to all of them in 5-10 minutes. Check out all the WDW menus on allearsnet.com. Look up Beach Club, Yacht Club, Boardwalk, Swan and Dolphin.