Of course RMNP is probably a must, and middle of Aug would be a nice time. Probably not as crowded as the summer peak.
Here in Loveland, Aug 10-12 is our annual Sculpture in the Park. So if you are here on those days, check it out.
Carter Lake doesn't really have a lot of hiking with the exception of THIS. But I'm also not sure what Carter is going to look like in Aug, it's been pretty drained last few years.
Just up the road from Carter is Pinewood, which has some hiking and probably less crowded.
On the other hand, I'd love to eliminate on street parking all together. Parking is complicated but there's some smart folks thinking really hard about it.
Here's an absolutely crazy book about it.
https://www.amazon.com/High-Cost-Free-Parking-Updated/dp/193236496X