Haven't been to Montana but I have fished around Estes Park... IMHO Estes has a couple of advantages.
First, its easier to get to... fly into Denver and its about 1.5 hours a way...
Second, there's lots of fishing inside the Park and a lot outside the park too. Lower Big Thompson, Cache La Poudre, South Platte (well, a little further) and a ton of small front range streams.
Third, as your wife is a non-fisher, there's lots of other things to do around Estes Park, in Boulder ( a short drive) and Denver ( a little longer driver), or Fort Collins...
Fourth, you can buy a really nice bamboo rod from Mike Clark in Lyons
Drawback is that Estes Park is very touristy with all the glitz that goes with that!
Plus, you can climb to the Continental Divide and pee into the Gulf of Mexico and the Pacific at the same time! Try that in Montana!