I bought a ticket... after spending a week trying to convince myself to sacrifice the Seaworld tour (that I already paid for), I realised tonight that I can do both if I have the energy for it.
The Seaworld tour starts at 8.15am, so I can spend about 5 hours there before I need to catch a taxi back to the hotel to get picked up at 2pm by IDW.
I'm so stupid for not realising that.

And if I do end up being so tired from the week of running around that I need a rest, I can just skip the Seaworld tour and sleep in that day.