Trains from NYC Penn Station run hourly, riding time 90 minutes each way. 2 bikes can be carried on either end of the double decker train cars, flipping seats up. You can secure your bikes with thin rope, sitting on seats across the aisle. Train begins at NYC Penn and ends at Trenton so you will not be rushed on and off. NJ Transit does not require a bike permit; one less hassle!
Online NJ Transit schedule: http://www.njtransit.com/sf/sf_servlet.srv?hdnPageAction=TrainTo
Note that NJ Transit senior ticket discount starts at age 62. Bring ID.
This is an easy, most unusual ride for NYCC riders. Except for access to the towpaths, you will only deal with motor traffic when roads cross the paths. The towpath surfaces are gravel. It is friendly to road bikes but wider tires are a nicer option if you have them. There is even a path going over Rt 29 on the NJ side at Washington Crossing State Park.
Caution is needed when passing under bridges while cycling north on the Delaware Canal towpaths. Be sure to gauge headroom as these vary. If in doubt either walk your bike or ridge to the right and cross the road off the bridge. Also, there are a few blind spots as you approach these underpasses. Be wary and respectful of oncoming path users. Another issue is crossing spillways on the Delaware Canal towpath (in Pennsylvania.) There will be times that some water will be spilling over them. Unless there have been recent rain of biblical proportions, you should easily be able to cycle thru these. The surfaces on these spillways are concrete; the surface is very rideable.
You might be well-served to print out the cue sheet for the Trenton/ New Hope - Lambertville / Trenton ride in this same Mid NJ South section as you might find yourself ahead of schedule and riding up to New Hope-Lambertville and back will add only another 10 to 12 more miles but add volumes to your day.
Bathroom stops and Cumberland Farms at half way noted on cue sheet.
The 2 streets you take in Trenton are safe other than motor traffic. You will pass the State Capitol Building and other historical sites in Trenton.
Go to these websites and read up on your history as this is all about Washington crossing the Delaware. Bring bike locks so that you can mosey thru visitor centers and take it all in.