I've never been to Banff, but I've been in Yellowstone and it is great, it's full of wildlife elks, mooses, bisons, bears, coyotes and so on, and they (except bears) will come so close to you that it would be very difficult not seiing them (oftne bisons sits on the roads of the park so you have just to get out of your car and begin shooting), landscape is amazing and just the geyser worth the trip.

If I were in you I'd use at least one day to photograph the north ring of the park, here there are the most of the geysers and they're quite close to the road so you don't have to hike for long distances, the southern ring has some geysers but there is more landscape, once done that start hiking in the interior.
Remember that the entire park is above 2000 meters over the sea level, I've been in august 4 years ago, at night and in early morning is very cold but at noon you can reach 30 degrees.

Just out of the northwest exit of the park there is Grand Teton national park, hiking in this park might be very difficult but there are some mountains shoots you can take without climbing 4000 meters high mountains that are worth the trip

I was wondering if it is safe to receive payments via checks, does anyone receive checks? have you ever had problems? i live in Italy is there someone non US that receive checks? haow long does it takes to get the check from the payout date?

I started with fotolia italy and approval times were near to 1 week, but from when I've passed to fotolia us approval times are very fast, from a couple of hours to  5 minutes or less.
Yesterday I've send some photos to dreamstime, they said there was an approval time of 4 days, but after few minutes i received mails for approved\non approved images

I've started with fotolia italy and approval times were about 7 days or more, now I've passed to fotlia us and now approval times are of few minutes, sometimes they are near to be in real time, is this normal in fotolia us or is it that today there are few photographs to be approved?

The main point is to avoid models being able to clam that they didn't know what they were signing, or they were drunk when they signed it

As for photo id's, if you can't tell easily what the age of the model is then you should get a photograph of their id to prove that you checked

I don't know how American laws regulates these situations, under Italian law (I'm Italian) if someone tells you that he is 18 and you, using and ordinary accuracy, can really believe he is 18, the contract is concluded and is valid it's a way to protect not only minors but even the ones who in bona-fide have been deceived by the minor.

Also for privacy laws I think that would be illegal to ask for ID's photos or scans, and normally a witness is requirede only for notary acts.

Now a question, in the contract betwenn me and the microstock agency is stated that me and the agency are under the law of United States, but the contract signed between me and the model is under italian law unless we have differently stated.

It is also stated that the agency is not responsible for copyrights infringements (and really I'm not sure it is a valid clause) and all responsabilities will be of the photographer, so why cannot I use my country laws to signs model release when any legal action from the model will not involve the agency?