Gwen Stefani & Blake Shelton Go Skiing, Tubing with Kids in Utah

Blake Shelton and Gwen Stefani are making up for some future lost time ahead of New Year's Eve -- when they'll be apart -- and did so by hitting the slopes with their kids.

The couple hit up Woodward Park City ski resort out in Utah Friday and Saturday with Gwen's 3 boys -- and the whole family was out and about, tubing one day ... and skiing the next. In photos obtained by TMZ, you can see GS and BS in lock step with the teens close behind.

Eyewitnesses tell us the family wasn't shying away from the attention they drew, nor were they opposed to taking pictures with fans ... by all accounts they were pretty cheerful.

Interestingly, it sounds like Gwen was the one going down the hills here -- on Friday, she could be seen tubing with her boys, while Blake looked on and filmed. On Saturday, she and the kiddos went skiing ... and we're told Blake did not attend. Seems she's the active one!

Anyway, like we said ... these love birds won't be by each other's side come midnight next week -- 'cause Blake's booked to perform in Nashville, and she got hired for a Vegas gig.