I would normally say try calling Marie Elliot at Bear Mountain Stables - (303) 588-2551
www.bearmtnstables.com/
but they are currently closed due to icy trail conditions. They might be able to do something on site though, if you still want to try calling. Marie is great!
"Now, more than ever, the illusions of division threaten our very existence. We all know the truth: more connects us than separates us. But in times of crisis the wise build bridges, while the foolish build barriers. We must find a way to look after one another as if we were one single tribe.” -King T'Challa, Black Panther
The truth is incontrovertible. Malice may attack it. ignorance may deride it, but in the end, there it is. ~Winston Churchill
If you can't score it up the hill and the kids are keen to ride, I'd take them down hill to Plum Creek. 285 to Santa Fe, south to Titan Road, take a right and it will be on the next corner up -- on the right side.
They have access to the most incredible trails -- going all the way to Chatfield. I've seen the most well-stuffed elk in the whole world, down in those draws.
It's likely the grandkids would like a smoother ride, and they will do that and birthday parties, all the bells and whistles.
Naturally I'd give them a call in advance just to be sure, and they will mount up just the right collection for those little 'uns of yours. Have a wonderful visit with the grandkids!! and a good time riding, wherever you find it easiest to do.