Regarding a rental. I drive AWD and FWD both with winter tires here in VT.
If the road is closed, it is closed. I have simply read a several comments about the difficulty of the drive up to Steamboat from Denver, and that both routes can be problematic. But I wanted some local knowledge to those claims.
If the crossovers and SUVs all have AWD that makes things easy enough, and it makes sense the online systems would not know the exact selection--they only guarantee "or similar."
Parents in CO mean flying into Steamboat directly is off the table, but renting away from the airport could be an option in Denver.
Do rentals at DEN get winter tires? Everything I have read, heard, and experienced puts way more value in a good set of tires than AWD when things get tough.