Chef Mickey's has Minnie and Mickey. Our family has done both the brekfast and dinner and they are both good. In the last few years, this has become a popular place, so make ADRs (or whatever they call them now) as early as you can to get a good time.
Cape May is a great character breakfast but we've never seen Mickey there. Minnie, Chip & Dale, & Pluto were there in their beach clothes on our visits. LTT has Minnie, Chip & Dale, Goofy, & Pluto--no Mickey. We did CM's a number of years ago & they were both there.
Birnbaum's 2006 Guide says that at Chef Mickey's they are both there for breakfast, but Minnie is not there at lunch (doesn't say about dinner, though).
It is possible at Chef Mickey's, Liberty Tree Tavern, or Cape May Cafe, but never guaranteed. It is more likely than not that you will have just one of the two mice.
You might be better off trying to get the fa- Mouse Couple (sorry it's late) at a character meet and greet. Early meet and greets at DAK aren't usually busy and that's when I've had the best luck seeing the two mice together.
They were both at the BBQ when we went, along with Goofy, Chip & Dale.
We've done Chef Mickey's 3 times. once with both mice, and once with Mickey, once with Minnie. Others roaming around on those trips included Goofy, Chip, Dale, Pluto & Donald (once). We only had Minnie at Liberty Tree Tavern, (with Pluto, Goofy, Chip & Dale) and Mickey at Garden Grill (with Pluto, Chip & Dale).
Both times we've done Chef Mickey's for supper, we've seen BOTH Mickey and Minnie. But at Disney as in life, there are no guarentees! I think CM might be the best bet, though...
The last time we were there - 4 years ago, they were both there. I remember because somehow Minnie got her "hand" caught in Chip or Dale's face and they both went tumbling into the kitchen. Very funny
Like everyone else has said though, no guarantees. Obviously things have changed since then which is good , gives us something new to look forward to.