I went to school in Ft. Collins. Horsetooth can be really good early. Just north of the fort there are a bunch of little lakes, most of them are private, but maybe he can get onto one of those..
Leaving Ft. Collins he'll take rt. 14 to Sterling.
There's a reservoir right there at the intersection of 14 & I-76. Don't know the name.
Right after I-76 merges with I-80 is Ogalla. Lake Mcconaughy is only a couple of miles north.
Good camping and really nice beaches.
http://www.lakemcconaughy.com/ I don't know much about the rest of NE or IA, I'm usually trying to get through as fast as I can.
I would probably stop in Davenport and ride the Mississippi. Take I-88 after Davenport and he could stop in Dixon and ride the Rock River.