Hello,
According to the hotel website, the bus stop at Fuji Q Highland is only 5 minutes by foot from Mystays Fuji Hotel.
If that is too far to walk with your baggage I suggest taking a taxi from the bus stop to the hotel. Telephone number to a taxi company operating in the Kawaguchiko area: 0120-818-229
If you still feel like changing the destination bus stop;
If you already payed for the ticket I recommend you to tell the ticket office before you get your ticket and board the bus. You could also ask the driver to let you get off at Kawaguchiko station.
If you did not pay for the ticket yet, you could cancel your reservation and make a new one to Kawaguchiko station instead.
Cancellation can be done on this page: http://highway-buses.jp/cancellation/
My reservation page: https://www.highwaybus.com/gp/inbound/inbRsvSearch
I hope this can help. Have a nice trip!
Didi