Looking at the map, it seems that there're several different ways one can go, so I'm wondering which is best. (AAA, oddly, is often not much help in questions like this.)
We'll be arriving at DIA around 4:30 on a Wednesday in early August. By the time we pick up our rental car (convenient at DIA, or a bit of a haul?), I suppose it'll be a particularly busy time on the roads; so we hope there'll be a route that can avoid the heaviest traffic.
In short, I'm hoping that folks familiar with the area can tell me which the best route would be to get from DIA to Estes Park. (We'll be staying at Boulder Brook.) By the way, after 3 nights at EP, we'll be heading to Boulder for another 3 nights, so perhaps it'd be interesting to head to RMNP on a different path from the one we'll be using to get from the Park to Boulder? Main consideration, though, should be ease of travel from airport to inn.
Thanks so much!

Take the tollway (470)from the airport to I25 north; go to Loveland and take 34 west into the park. The trip back to Boulder will be on 36, which goes thorugh Lyons. The way to RMNP via 34 is simple enough; there is a scenic alternative to 36 to Boulder, if you want to spend a little more time: 7 to 72 [through Allenspark, Ward, then Nederland], then down Boulder Canyon on 119.
I would avoid taking 36 through Boulder on your way to the park; traffic can be awful on the turnpike (36), terrible in Boulder, and there is major construction on 36 in Lyons this summer.

Thank you, sylvia3!

Do you realize that you're talking about a several hour drive after you get off your plane?

Tis true!!

Even taking sylvia3's route from DIA to Estes Park, it's still about a 2 hour drive - but I'd suggest taking it.

Got caught in the construction along Hwy 36 before and after Lyons myself yesterday on my way to RMNP.

Thanks for chiming in. I'm glad to have it confirmed that the drive will be at least 2 hrs. I.e. I wish it were shorter of course, but the inn's estimate of hour and a half just didn't seem correct to me. At least now we'll know what we're in for. Thanks again.

It's a pretty easy drive, though; if you were driving very fast, in daylight, and knew where you were going, it could take less time.

The inn's estimate of 90 minutes is correct - the drive from the car rental car area at DIA to Boulder Brook is no more than 90 minutes if there are no traffic jams. By 5:30-6:00 pm when you're getting on the road, traffic shouldn't be a problem, plus you're not driving through the downtown area, but getting on I-25 on the northern outskirts. It's an easy drive on E470/I-25/Hwy 34, no mountain passes. You'll be in Loveland in 45 minutes or less, then another 45 through the Big Thompson Canyon into Estes. When we drive back from Estes to Littleton (way southwest of Denver), we take this route and it's less than two hours for us, with more miles through the city. Should be a wonderful time of day to start out your trip!