I'm not sure what that's for, as baggage check-in must be done 45 minutes prior to boarding. Now at Vacouver, BC; Seattle, and Portland they do check-in prior to boarding and assign seats. But at Bellingham they'd have no way of assigning seats, as they have no way of knowing what seats are even open.

Regardless, you should still be good with even a 5 minute window. Only the conductor on the train can really "check-in" someone.