No reservations at ESPN Club. You could plan to do this on a day you are at Epcot. Just exit through the International Gateway located between United Kingdom and France. Give a "gee honey, let's see what's out here" thing. Once outside the turnstyle, make a left and cross over to the Boardwalk. He'll probably hear the ESPN theme before he sees the restaurant. Unless it's a sports day, I'd go after 1:00 for a nice lunch. Don't go on a Sunday. Yes, it's a fun atmosphere but you'll have to stand in a huge line to get in. During the week would be much better.
Encourage him to get up and walk around and look at all the stuff on the walls. And yes, definitely make him go to the bathroom while he's there! There's also a nice gift shop next door so maybe you could get him something to remember your surprise.