there is no reason to think the tour buses will return from the causeway to the visitor center after a scrub. they're almost certainly going to leave the causeway and go straight back to orlando or cocoa beach or wherever you were picked up.
here's what the KSCVC parking lot is like for hours after either a launch or a scrub: a completely bottlenecked single lane of KSCVC buses entering the main bus loop from the causeway, to drop off those who bought tickets online and drove onto the premises with a parking placard, and a completely bottlenecked single lane of cars with parking placards trying to leave the main parking area. traffic in gets waved through by police, and then they come to a stop while traffic out gets waved through by police.
here's the way tour buses operate:
1. you're picked up at a designated parking lot somewhere in florida at a designated time by a tour bus and transported to the KSCVC.
2. you exit the bus with all your gear and feed your blue KSCVC ticket through a turnstile, which is returned to you when you walk through.
3. you go through metal detectors and bag screening, and spend a few hours in the visitor center while your bus is being screened by security.
4. a few hours before the scheduled launch, you and your already-screened gear are picked up inside the KSCVC grounds by your already-screened bus. you hand your LTT to an employee while in line to board the bus. from this moment on, you have nothing but a blue ticket good for one more day at the visitor center. as clearly stated in section 7.A.1 on the kennedy space center web site at
http://www.kennedyspacecenter.com/LTT.aspx, that's it. whatever happens after you board the bus to the causeway and surrender your LTT, your ticket has been used and KSCVC's obligation to you has been fulfilled.
5. your bus takes you to the causeway. the launch happens, or it does not.
6. your bus leaves the causeway and returns you to your designated parking lot.
people sometimes get confused on this point because bus tour attendees take a bus to the KSCVC and then board that same bus to the causeway a few hours later. "If you board a bus to the NASA Causeway and launch is postponed," proclaims the kennedy space center web site, "all elements of this ticket are considered used in full." by "board a bus" they're referring to step 4, not step 1.
the policies on the dolphin web site are badly written, because there should be an additional category listed after "In the event of a scrub/cancellation/reschedule at KSCVC" titled "In the event of a scrub/cancellation/reschedule
after giving up your LTT and leaving the KSCVC for the causeway," covering steps 4-6.
both dolphin policies quoted above describe steps 1-3, scenarios where you are either on your way to the KSCVC and have not yet surrendered your LTT, or after you have arrived at the KSCVC --
and have also not yet surrendered your LTT (step 4). in either scenario, enjoying KSCVC "as a regular day" is still an option because you're either approaching or have arrived at the KSCVC but have not left for the causeway yet.
i have never heard of tour buses returning from the causeway to the KSCVC after a scrub. my experience after STS-128's weather scrub was that the gator tour bus went straight back to orlando. friends who took gator tours to STS-130 reported the same result after its weather scrub.
as relayed elsewhere in this thread, KSCVC has, in the past, given out vouchers for people boarding
their buses (orange tickets, purchased online) to purchase replacement LTTs upon return to the KSCVC. their buses do return to the KSCVC, because all of the people on them arrived at the KSCVC by car, using the parking placards that were sent to them with their tickets. the handing out of vouchers is not a stated policy on their web site and is not guaranteed to happen at all for this last scheduled launch of atlantis. if anything, handing out vouchers at all in the past has been going well above and beyond what they're obligated to do.
my experience has been that gator tours does not give out these vouchers, because they head straight back to orlando after a scrub. on the bus ride home, people are offered either an opportunity to purchase return roundtrip tickets to view the launch from the visitor center with the second half of their blue ticket, or an opportunity to purchase return roundtrip tickets AND replacement LTTs, which has not been offered every time.
i have never taken dolphin or central florida bus packages. but i can't imagine they work differently from gator in this respect.