Moraine Park is a great place to fish, and it sounds like you will be camping close by. I've never camped at Aspen Glen.
There is some heavy road construction happening close to the Moraine Park area. So my best recommendation would be to research (call and email/txt) about the current conditions of the road and access.
Have a nice day.......and as always.....report what you hear on this site
As far as what flies to fish......it's a small river/stream in the West. Typical stuff will suffice. Para adams, Griffith's gnat, wooly worms, etc is all you shall need.
Have a nice day fishing.