When I was there last weekend, I was being seated at 50's Prime Time Cafe when my boarding group was called. Since the window is 2 hours, we ate lunch like normal and still had about 50 minutes to get to the ride.
When we got off the ride, we were 25 minutes late for our reservation at Oga's Cantina, and when we explained why we were late, they were very accommodating and still let us in (with another wait of approximately 20 minutes).
So I wouldn't worry about it too much. I would use the entire 2 hour window if necessary and let the restaurant reservation times be more like guide lines.
I went two weeks ago and had a reservation for Oga's at 11:20, then a reservation for Savi's Lightsaber at 12:50. My boarding group was called at 10:20. Scared of missing one of my reservations for a potentially long line I asked one of the people working the front of Oga's what I should do, and they said immediately in character, "Look, I haven't seen Oga around yet today, how about we just get you in there now. What do you think Oga would prefer; being early or late?"
Thanks to you both for sharing your experiences. Glad to hear they were accommodating. I know it’s a bit silly to worry about a bunch of tiny “what if’s” but it is reassuring to know it’ll work out.