Part of your large route goes through Apex Park. Those trails would not be suitable for a road bike. Instead, you should take US 40 up the Mt Vernon canyon. I made some edits to your map: http://maps.google.com/maps/ms?ie=UTF&msa=0&msid=216879053703708317241.0004c7e543ac4ce2efb58
Besides avoiding Apex Park, I improved your route through Bear Creek Lake Park.
Climbing Mt Vernon Canyon at the end of that ride may be a lot to bite off coming from low elevation.
The Cherry Creek and Platte River bike paths are highly recommended. Your route already includes half of the Platte Trail. It's popular to link the Cherry Creek and Platte Trails with the (less recommended) 470 bike path to make a ~60 mile loop.
One more thing, the NE section of your route is pretty industrial and not very scenic. Most riders would get to downtown from your starting location along 32nd avenue.