I actually found long distance runs to be tough.
There are a bunch of options for runs of a few kilometers, but looking at my training schedule, I'd estimate that he'd be doing around 25km by the end of August (give or take). So, he may be looking at lots of loops!
I know from personal experience that running on 'main roads' may results in an offer of a lift from a passing bus driver - an offer that he wouldn't let me refuse. Not sure what rules (if any) I was breaking but two different bus drivers insisted that I couldn't be on the road - I was somewhere just outside of Coronado Springs.
Tell you DH to enjoy NYC - I ran it in 2005 and loved it.