I used a pair of Audiovox FRS radios last winter for the drive down to IAAPA between cars. Between cars they worked great, but watch the battery life. In the convention hall they were less useful, and at Dollywood they worked fairly welll, but did not give us full-park coverage.
Of course, Cedar Point is much flatter than Dollywood, which should help. I suggest doing some tests. If you have not bought your radios yet, I suggest you investigate the ones with the privacy codes (CTSC or whatever it is) as FRS radios are popular and becoming more so. Mine don't have the codes, and sometimes I find myself wishing they did...
--Dave Althoff, Jr.