Didn't spend too much time up in Kahuku but used to kitesurf at Hukilau Beach a fair bit. Nice and quiet up there. Nice to hear they have a bike path now.
Are you able to carry your bike around Kaena Pt? I seem to remember the road was completely washed out in one section and you had to climb the cliff there. Would be challenging with a mb. Watch out also for the road between Ala Moana and Hawaii Kai. I got hit by a car on Diamond Head Road, and a buddy got creamed by a car in Aina Haina. I've also witnessed tons of moped vs. car accidents in Waikiki.