Kyle Richards Had Dinner with Mauricio Umansky & Family in Aspen

Kyle Richards and Mauricio Umansky are playing nice and eating nice -- especially in the presence of their kids ... which is exactly how they ended their day in Aspen.

The estranged couple broke bread together with their daughters Saturday out there in Colorado, where the family of 6 sat down at a table inside Matsuhisa and chowed down on sushi after a day of skiing up and down the snowy mountains.

In photos obtained by TMZ, you can see mom and dad were actually right next to each other during the meal -- and eyewitnesses tell us they looked cordial too ... no apparent animosity.

In fact, we're told they even spoke to one another a few times throughout their time there ... this while the kids were distracted on their phones. So, on its face -- a chill evening.

Pretty interesting, especially when you account for Mauricio's wild time 2 days before Kyle's arrival ... when he was partying shirtless and hanging with bona fide hotties on the slopes.

Truth be told, it's hard to gauge where things stand between him and KR ... but they certainly don't seem to be romantically involved. Perhaps they're just coparenting through the separation and trying to maintain normalcy in household as best they can.