I'm assuming you are talking about the Fantasmic! show in MGM? There is an afternoon parade. You should probably plan on about an hour to eat. Sure, it can be done quicker, but it's better to plan for a longer time. It will then take you about 8-10 minutes to get to the International Gateway where the boats to MGM are. Now....best case scenario? You get to the boat just as it is loading. But it will make stops along the way, so it could take you 30 minutes to get to MGM. So, if you have to wait for a boat, then add on travel time you could be looking at 45-60 mins. You could walk all the way. I have made it in 18 minutes from the Intl. Gtway...but I was really moving. If you decide on walking...head towards BW from the Intl Gtwy....as you walk up the hill, go to the left. This will take you to BW. Now, when you get to the area on the Boardwalk where the surrey bike rental area is...this is called the Village Green...head off to the right towards Wyland Gallery. There will be a tunnel/walkway that will take you to the pool area. Muscles and Bustles health club and the Arcade will be on your left. Stay to the left of the pool area and head toward the canal, which is behind the pool. When you get to the canal walkway, go left and you'll be on your way to MGM. It sounds a bit convoluted but it really is easy once you get there and see what I'm talking about. The walk is about 25 mins from the Intl. Gtwy...give or take. It takes me about 15 mins from BW to get to MGM. Once you get to MGM it will take you another 8 mins or so to get to the Fanstasmic! stadium. And it can be crowded, so most people like to get there at least 30 minutes before showtime.
So, all in all....you may be cutting it too close. Wow...that was a lenghty way to say that wasn't it??!!!