Meet at alligator p's trailer @ vendor row. 
The only problem i see w/ bikes leaving at noon is White Wash of the dunes.. Pain in the butt to read them and see for that matter.  I would have to say Bikes 9-10am and buggys 2-3pm  a morning and afternoon type thing...   That gives the bikes time to get back (and if they have buggies as many do, get ready for the buggy ride), then have a bite to eat and off for the buggy ride.