First of all, I want to honor the fact that you care for how your new wife will experience the Glacier trip. Some guys don't think that way. Also, the others have posted some sage advice for you.
I grew up next to GNP, have hiked most of its trails over the years, and in '06 slammed five 3-5 night trips back to back. I'm curious as to what your ininerary is. Some trails are more rugged than others, and the Highline trail NW of Granite Park can be downright suicidal some years. Generally, in August the snowfields will have melted, but you'll want to talk with the rangers regarding whether you'll have cascades or snowfields to negotiate. I've found that having trekking poles along help greatly in both cases. Ice axes or crampons are not needed.
The past several years, the low temps in July have been 45-50 degrees, and in early-mid August maybe 38-45 F. But later in August, as the long days get shorter, there can be some colder nights. I've found that my +15 F bag has been an overkill up until maybe the last week of August. If you are thinking of investing in a great, expensive bag for your wife, you might want to consider Marmot's Hydrogen (+30 F) or their Helium (+15 F). Those 850+ fill bags had a 1/2 length zipper through '07, which made it impossible to open up fully on a warm night. However the '08 models now have a nearly full-length zipper, which will make them more adaptable to a range of conditions. If you want another tent, and not a single wall, you might look at Marmot's new Aura 2P. It's a light little sucker, at a trail weight of 4# 12 oz, 2 vestibules, and structurally sound. I like mine because it actually has enough length for my 6' frame. It just has a 50" width though, not a huge living space. I don't work for Marmot, by the way--I just like some of their stuff. And if you are an REI member, you can score a 20% discount on one of these until March 31.
Canister stove: If you have already won the lottery and want to buy more gear, you might give the JetBoil a try. It's quite a bit more economical fuel-wise, and I bet you could get by for those 6 days on one 8-oz.(fuel weight) MSR IsoPro canister (my vote would be to also take a small (4 oz. fuel weight) Snow Peak or JB canister as a backup). MSR's large 8 oz canister, when full, weighs ~3/4 oz. less than a Primus canister. However, MSR's 4 oz. canister
weighs ~1.0 oz. more than Snow Peak's.
Other miscellaneous thoughts:
1) Some GNP campsites do allow wood burning. This will allow you to boil water for your meals and save some cartridge fuel. But it doesn't get dark up there until after 10 PM, so you won't need a fire for entertainment.
2) Don't forget your DEET--the deer flies and mossies can be horrendous up until the first week of August.
3) Bear protection: I usually carry one small Counter Assault and one 4 oz. miniature fog horn. The sound that little air horn puts out will chase off any self-respecting black bear, and it also will work nicely as a distress signal (when it's too windy for your whistle to carry very far). I think the best book on griz behavior is the one by Steven Herrero. You can read it at work so your wife doesn't get scared. The main thing is to hang everything that has an odor (toothpaste, all cosmetics, EVERYTHING!)along with your food bag. Nothing at all goes into the tent with you, except a flashlight and your bear spray. And when you hike, make noise, chatter, sing Jimmy Buffett songs, etc. Forget about bear bells--they don't make enough noise to warn an animal that you are coming, especially on a windy day, or while walking along a river.
If you're in St. Mary, grab a meal at the Park Cafe. Everything is splendid, except the long wait.
At the Many Glacier Hotel, park in the lot above the hotel, grab a beer from your cooler, and sit on the hill at sunset overlooking the hotel and one of the planet's finest scenes. Then snag a bison steak at the Cattle Company back where you turned off hwy. 89 to get to Many Glacier.
Back in Kalispell, you have to celebrate at Moose's Saloon on the north end of Main Street.
I hope you enjoy my home turf. I always thought that when I became king, I would take over the place for my very own...and outlaw mean people, al-Qaeda types, and the like. You'd have to be a BPL member to get in.