Here's a good reason to not sell it: You need at least the next 6 months to think about it.
Not good to sell a bike as autumn is coming up -- lower prices unless you're a dealership and can add incentives. It's always better to sell in the spring -- but that's impossible because you realize how wonderful it is to ride it.
Best solution -- keep it.
Where there's a will there's a way and with CraigsList.com, you can find the nephews some inexpensive motorcross bikes to get them going!
Besides, think about how sad you'll feel when you hear the sound of a Harley motor pull up next to you and you don't have one! Tragic.