I'll limit this to lunches as I'm sure others will cover the dinner options.

My top 2 Marigot lunch spots are Tropicana and Be Kool. Try to do both. Le Bistro Nu is also a good choice.

I'm not sure there are too many non-lolos doing lunch in Grand Case, but my top 3 choices would be Nice, Villa Royale, and mussels at Sunset Cafe (Order on Thursdays for Friday). Ocean 82 may be doing lunch, so that would also be an option.