You've been typing what I've been thinking all day today.

Although in this case you could cut this all down by an hour by scheduling Splash and Thunder both from 11-12 and as soon as you scan at Splash, transfer Thunder (while in the window). Heck, you could even make the final 3 FPP's (CPFP) 1.5 hours earlier (using your same first initial 3):
10:30 BTMR
11:30 HM
12:30 PP
Ride Pirates right at 10. Get to Splash right at 11 (10:55 actually) and as soon as you scan transfer BTMR (you'd still be in the window 10:30-11:30). As soon as you scan at BTMR (assume right at the end of the window around 11:30), transfer the HM. You'd still easily make it there before 12:30 (maybe even grab lunch on the way). And you'd scan the last ride (PP) right at 12:30. Doesn't take any longer than before. I'd probably put the ride you care least about at 10:30 on the "transfer" band, just in case timing works out and you don't make it, but as discussed, you have 15 minutes leeway, plus if you're a couple minutes past that, the CM's will undoubtedly wave you through.