Hi Pam,
One of the hard parts about keeping these replies pertinent is the fact that I cannot see your most recent post with all your very good questions (are you listening TA staff??) but here goes anyway:
Your question about staying in two different places in Bigfork is a good one. I wonder why you are choosing to move locations by only about 3 miles. Maybe consider making a move up to Whitefish, about a 40 minute drive from Bigfork, and dividing your time between these two lovely villages/towns. Both places you have selected in Bigfork are lovely. Both very different, but equally nice. The cottages will allow anyone in your group to walk around town. The Lodge has some nice walking along Sylvan Drive (my old neighborhood) but this is simply a quiet street to walk along...no shops or anything of that nature. You would need the car to get to any other areas.
Find the Swan River Nature Trail above the town of Bigfork (walk up hill from the Two Rivers Gear). This is a nice wide walking trail that is easy for 4 people to stroll along and enjoy the views.
Two Rivers Gear in Bigfork can arrange a guided fishing trip: 406-837-3474. A-Able Fishing in Bigfork takes folks out on Flathead Lake: 406-257-5214.
While in Bigfork, do find your way to the Echo Lake Cafe on the outskirts of Bigfork. Breakfast or lunch (closes at 2:30) weekends there's always a wait, relax and read the paper,soak in the local ambience of a successful restaurant "out in the middle of nowhere".
The best spa experience I can think of would be at the Lodge at Whitefish Lake, although if you call any of our Chamber of Commerces, you will find more. The Lodge would be the classiest place.
There are also fishing charters in Whitefish (Lakestream Fly Fishing Shop, 862-1296 (all phones, yes, all, in MT are area code 406)
There are also more adventure sports at the ski resort above Whitefish, used to be called Big Mountain but they renamed it something like Whitefish Mountain....gondola rides, Walk in the Treetops, but no hot air balloon rides that I know of. So do think about splitting your time between BF and WF for more diverse experiences.
As for historic areas, go check out the eastside of Kalispell. There is a great walking tour of historic houses, the Conrad Mansion, the Central School Museum. Since Kalispell is right between Bigfork and Whitefish, you will be going through it as you travel from one to the other.
I'd skip the long drive out to Lake Koocanusa. It's not all that lovely of a lake. You'll get much better scenery in Glacier NP.
CampingGirl is our helpful TA expert for Waterton. You are right in saving your boating trips for Waterton (Glacier too, if you like more of them). BRING PASSPORTS for getting in and out of Canada. Make sure your car rental co. is OK with that.
Your return drive from Waterton back to Missoula might be a bit too long for one day, IMHO. At the beginning of your trip, I recommend that you travel from Missoula to Bigfork on Hwy 93 (there is road construction for about 10 miles right as you start on your northbound journey, so relax, nothing you can do about this). This route will give your breath-taking views of the Mission Mountains, esp. around St. Ignatious, then the awe-inspiring view of Flathead Lake as you enter Polson, then head up the east shore of the lake to Bigfork.
For your return journey, think about taking the Swan Highway, Hwy 83, from the Bigfork area all the way down to Clearwater Junction, then head west to Missoula. It's not nearly as populated, and it's a beautiful drive. You may wish to overnight at the Laughing Horse Lodge, and treat yourself to some of Kathleen's cooking. From there, you'd be about 2 to 2 1/2 hours to MSO, if that fits your flight schedule. And, no road construction! Do watch for deer on Hwy 83.
You don't say what month you will be here. If it's anywhere near the end of July, beginning of August, you will be in for a treat: some of the best cherries in the world grow all along Flathead Lake.
OK, Pivan...see what this does for your trip planning. One more hint: call the Kalispell Chamber of Commerce and ask them to mail you a copy of "101 Things To Do in the Flathead". You can then customize your time here based on the weather, what your interests are, and what strikes your mood when you are actually here.
Kudos to you for making a plan that includes visiting areas around the Flathead Valley in addition to the gorgeous Glacier National Park.
You're going to really enjoy this visit!