Transportation can be a challenge in Glacier. If you have ideas, offer ride shares, or used a commercial service that you were happy with, let everyone know. Also, ask questions about road information, or share road information you may have.
If you're worrying about the busses selling out, I think you should be okay. But I also think you can make an advance reservation as well, just to be sure.
So, what have you got planned for your seven days in the Many Glacier area? Is this your first time?
I, along with many others here, am happy to offer suggestions and advice. Just let us know what you are interested in doing. Since you are staying several nights at MGH, I assume you aren't going to do any camping or backcountry hiking. But what about day-hiking? If so, any particular distances or levels of difficulty? Or are you more into sightseeing from your vehicle? Would you be interested in horseback trips? Boat rides on the lakes? There are lots of options, so just let us know where your interests lie.
Hockey Ref
"No man lies on his death bed wishing he'd spent more time at the office...or getting chemo."