It sort of makes your head spin, doesn't it?
I'm generally not a big prime user, so I'd go with the 24-70 and leave the 45 behind. But I haven't shot with the 45 and can completely understand an irrational attachment to a specific lens.
I finally decided a couple years ago to bring 2 backpacks when I fly somewhere. I have one with wheels that I use on travel day. Huge help! But it's not comfortable to wear on my back for long periods of time, so I put an empty comfortable backpack inside my suitcase to use once I arrive and carry less stuff day to day.
I considered doing something like that. But I figure limited myself to one fair sized camera bag is a way to force myself, to not overdo it. Though I do think my 70-200/4 will just go in a suitcase.
I'll be using the 45 for dark rides. So it's definitely coming. If I wasn't doing dark rides, then I likely would take the 24-70 and leave the 45 around.
Also undecided on a tripod... I have a small gorrilapod for the A6300. Undecided whether to also bring a full tripod.
Here is my dilemma --- For telephoto at Animal Kingdom (possibly the only telephoto I'll do on the trip), I'm happy with the A6300. So I'm not bringing a telephoto lens for the D750.
For dark rides, I want the D750 and 45/1.8. If I really don't want to carry the D750 on a given day, and a dark ride pops up, I can use the A6300 and 24/1.8.
Problem is areas where they are really duplicative --- I totally intend to use the A6300 for some wide landscapes. It does well in good light, it is really small and easy to carry with the 10-18. And with the gorrilapod, it is very useful for fireworks and long exposure night shots.
....... but... the D750 is a tad better for landscapes, especially at sunrise/sunset, etc. The lenses are a bit sharper, and I get a lot more dynamic range to play with in post. But do I really want to carry an APS-C ultrawide lens AND a full frame ultrawide lens? And that might mean the need to carry a full tripod as well......
Okay, I've just answered my own question, I think. The Nikon 18-35 works pretty well on the A6300 with adapter. So it's ultrawide on the D750 and basically a normal walk around lens if used on the A6300...
My 45/1.8 also works ok on the A6300.. focus can take a half a second. Same with my 85/1.8 -- Maybe I should only take Nikon lenses that can serve a dual purpose -- also be used on the Sony.
Ok..... subject to a million more revisions:
D750 + A6300
Sony only lenses: 10-18/4, 24/1.8 and 70-200/4
Nikon lenses that can be adapted: 18-35, 45/1.8 and 85/1.8
1 speedlight
1 gorillapod (I'll make do without a full tripod)
Camera bag can probably hold the 2 bodies, 4 or 5 of the lenses and the speedlight. The 70-200/4 will go into a suitcase, only being pulled out for Animal Kingdom and maybe Fantasmic.
Camera bag, on cruise ship, at sea: D750 + 18-35 + 45/1.8 + 85/1.8 + speedlight
Camera bag excursions: A6300, lens adapter, 10-18, 18-35 and maybe the 70-200.
Magic Kingdom mornings: A6300 + 10-18, D750 + 45/1.8, maybe a speedlight. Yes, it's 2 camera bodies, but only 2 lenses. (maybe toss in the 24/1.8 for the Sony)
Animal Kingdom: A6300 + 10-18 + 24/1.8 + 70-200.
Nights... we will be doing Epcot and DHS... So for nighttime fireworks and long exposure night shots at those parks, the A6300 + goriliapod + 10-18 + 24/1.8. May or may not also bring D750 + 45/1.8 depending on whether Im planning any dark rides and whether I feel like carrying the weight.
... I think I've got a plan!