You should be fine on all-seasons for the couple days you're there, generally winter weather is quite sunny and road conditions improve pretty quickly after snowfall. Lots of winter visitors drive to the mountains in rental cars, which definitely don't have snow tires. However... in case of a severe storm (not uncommon), you should:
- Familiarize yourself with Colorado's traction laws -
https://www.codot.gov/travel/winter-driving/assets/FactSheetTractionandPassengerVehicleChainLaw.pdf
In the worst conditions, your FWD CX-5 will not be legal without chains or an alternative traction device. I also would not recommend driving a FWD car without true snow tires even in "traction law" conditions, which is a step down from chain law. Also, in really bad storms sections of I-70 and other mountain passes are closed down making it tough to get to Breck.
- If it is snowing, even lightly, give yourself PLENTY of following distance, and then give yourself 2x more following distance than you think you need. A common winter driving mistake is when people feel like their car accelerates just fine, they think it will stop just as well. All-season tires generally have very poor stopping performance in snow, especially if they are worn.