While it's true that most Shimano 10-speed shifters work with 9-speed mountain bike derailleurs, the 4700 series shifters do not. They changed the shift cable pull for the 4700-series Tiagra parts.

On the other hand, 4600/5700/6700 would work for a 9-speed rear derailleur. You can find the M591 on eBay, and it is designed to work with a 36T big cog. I'm inclined to believe that you could get any of the shifters I just mentioned to work with the XT double crank you described using a front derailleur designed for a compact double. As Andy Stewart mentioned it might be a little finicky, but you could probably make it work. Apart from how it shifts, the chainline would be less than ideal. I doubt it would be bad enough to cause problems, but you might have some issues shifting between the bigger cogs while using the big chainring.

Personally, I'm a big fan of triples and I think that would be the way to go. You can put a 24T ring on most triple cranksets and use it as a bailout gear. Most of the time you'd just be switching between the middle and big rings, so it's not a lot more complicated than a double. I say "most" triple cranksets will take a 24T because recent Shimano has decided it would be a good idea to bolt the small ring directly to the middle ring, which generally limits your options. IMO, the 5703 crankset (still commonly available new) is the best option among Shimano cranks. On the other hand, you can get a Stronglight triple for around $60. It has lower gearing to start with and uses a square taper bottom bracket.

The Gevenalle shifters mentioned earlier are also very nice. They make front shifting much better, and you won't find more dependable shifters. They also offer a model which is designed to work with Dyna-Sys (10+ speed) mountain bike rear derailleurs, so you can get the fancy new technologies like Shadow Plus. Also, if your bike has cantilever studs, you can get Gevenalle levers that have the right cable pull to use V-brakes without a travel agent (a big step up from cantilevers IMO).