the only place I can think of is the dining package at Lombard Seafood, but TBH I wouldn't pay extra (even with meal included) to watch that show ... not worth it.
I have not watched it from there, but Duff Gardens may fit the bill well. I've watched from London and Richter Burger. Richter Burger offered a nice quiet place to watch the show but nothing was open near by to grab a drink. I don't remember if anything was open in the London Waterfront area.
I'd probably get something to drink (Butterbeer or Beer) in Diagon Alley and then exit that area to look for a place to relax. The two nights we were in the park this month we only caught the tail end of the show twice (we'd been on rides before it started) and just watched as we walked along the waterfront as we walked out of the park.
I like the central park area down from the Back to the Future car and train. Sit on a rock, lean on the railing, one of the screens is right in front of you.
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