Check with Al I'm sure you can leave a truck in the parking lot at the Tanglewood or even go a bit North up H58 and talk to the Bear Trap they have a large lot as well. If you were just looking for the day I would agree with the Kingston Plains but it seems like if rigs are left there for any length of time guys come back to things missing. You could also look at jack Pine Lodge a little south on M94 talk to Kevin the owner he has a lot of parking and will probably be fine leaving a rig there. Also you could check with the Cherrywood in Wetmore as well not sure if they would be as open to leaving a rig there since they are a hotel but they are very nice people and cater to the snowmobilers and have a lot of parking. I left a truck there for three days but we also rented a sled from them.
Good luck!!