Minnie Van is part of the Lyft app. If you open the Lyft app while on Disney property, you will only see the normal Lyft options. However, if you stay at a participating resort, then a new option appears in Lyft for Minnie Van. They originally said a code was required to get the Minnie Van option to appear in Lyft. While we were in the Kidani lobby, I opened the Lyft app. Minnie Van now appeared. I did not need to type in a code, or link a reservation number. It just appeared. This could have been a fluk, but I think it is the just the way it works.
Once I left Kidani, the Minnie Van option continued to be available, regardless of where I was on property.
So, a day or two in advance, walk over to BWI, and open the Lyft app. See if the Minnie Van option appears. If not, it can't hurt to ask someone. I would be interested to know if this works all the time, or maybe we were just a oddity.