Hi, sounds like they're in for quite the adventure! I'm a born and raised Alaskan...I'll see if I can answer any of your questions...
It says they'll end up in Skagway...what other areas will they be in?
I would look into state campgrounds. Will they be tent camping or motor home? That will make a difference in fees...
Here is a campground link:
Find a Park, Campgrounds, Alaska State Parks
Reservations, though it may sound a little odd, are not a bad idea.
Here is the fees link for State Campgrounds - 2010 (no, not cheap):
http://dnr.alaska.gov/parks/asp/feesfs.pdf
There are MANY privately run campgrounds...googling for those works great! The campground hosts are usually really friendly and a wealth of information. Often these places will send you free info in the mail (state will, too).
Make sure they have a LOT of bug dope! The joke is that the Alaska state bird is the mosquito. They are BIG and there are MANY of them.
And, though it's a sensitive subject, I would highly recommend having a gun as part of their camping supplies. Alaska is a rugged place and can be very, very dangerous...yes, even within the campgrounds.
Summer is what we call "tourist season"...things will be busy in the fishing areas, so be prepared for that aspect of it, and prices are always higher during the summer. If they'll be cooking at their campsites, it's best to stock up on supplies in the larger areas...Anchorage, Kenai, Soldotna, etc. (not sure where exactly they'll be). I assume they'll be driving? Gas is usually in the $4.25 - $4.50/gallon range over the summers (running about $3.40/gal right now in the "big city"...higher prices the farther you get away from the main 'hub' areas).
If they're fishing they'll need fishing licenses, but that can be a way to defray food costs! =)
If you have more details I can try to get more specific about things...

Sadly, "frugal" and "Alaska" aren't 2 words I would tend to put in the same sentence.
