Diehard MC fans know the singer's known for taking this yearly trip with the kiddos, but with the pandemic still raging out of control ... the singer wanted to find a safe way to make the trip without taking to the sky. The solution? Hitting the road in a luxury RV.

We're told she kept the yearly tradition alive by renting a 2020 Prevost RV through Outdoorsy.com -- it's like the Rolls Royce of RVs -- and decking it out with Christmas decorations like wreaths and poinsettias before embarking on the 5-day trek. They ventured across a must-see scenic route that included stops in Red Rock Canyon and Zion before arriving Wednesday in Aspen.

The RV's pretty sick ... with 2 bedrooms. a spacious living area, full kitchen and multiple bathrooms. This kind of RV usually rents out for $150k a month ... so you know it's top of the line and very much Mimi-approved.

Mariah's been going to Aspen for a long time ... telling GQ last year she goes because she loves a snowy environment, gazing at the mountains and spotting shooting stars. The kiddos also interact with live reindeer and even Santa Claus pays a visit.