Usually adrenelin sends blood sugar up, it's counter regulatory to insulin. There could always be a strange response where roller coasters send you low, or walking round Blackpool does. So you'll just have to see what happens and deal with it on the day. If it does send you up correct very cautiously - query the PDM corrections - because as soon as you are back on solid ground the adrenalin can disappear and there might be no reason to correct.
I've not seen anything about pods and roller coasters. I'm sure it'll be fine. Maybe just try to stick it somewhere it's not likely to be got by the seat harnesses.
I don't use the libre, but that'll probably be fine too. Maybe have a quick check on the Abbott site.