Lots of choices for bikes which come with free optional helmets for adults. For kids under 16 its law. Hard to find this place but heading north, its on the far edge of of Kapaa town, just pass the ocean side soccer field. The trail is awesome and if you wish to ride south, you can connect up with the second addition of the trail for a great ride more than 5 miles. Just ask at the desk, staff are very knowledgeable. Half day rentals are for 4 hours from when you rent, for about $18 each.
Would use these bikes again.