the hike to granite park chalet is great. its about 8 miles each way but not too uphill. thats the one i made mason go on when he came up to montana. it starts at the top of the pass on the sun road.

or from near where they are camping they can go to sperry park chalet and the glacier up there. its a grunt up but really nice when you get above the tree line. very good trail as horses use it during the tourist season. if they are really in shape they can continue on toward gunsite pass where it may be the best spot on earth. both hikes can be all day long ones .