First, happy anniversary!
Second, I love that you are doing this! It sounds like exactly something my DH and I would try to do too!
I think that no matter what you end up doing, as long as you can stay relaxed and go with the flow, you’ll be great.
If you haven’t seen Pandora yet and really *want* to try to get on Flights of Passage (oh yes, I think you should try), my only suggestion would be to flip everything.
You already recognized that you might be better served to get to a park closer to rope drop vs heading to AK 2 to 2.5 hours after they open. I would drive to DHS and hit your highlights – boat or walk to EPCOT (I know, earlier in the day than you anticipated), enter via IG – drink and/or snack if you’re wanting something from World Showcase, stroll up toward Future World and hit Soarin’ and/or Test Track (single rider if necessary, or FastPass) – monorail to MK to spend your time there – Uber back to DHS to pick up car and drive to AK – Pandora in the evening/night – AK is open until 10 pm, so you could try getting in line near closing time for a bearable wait (I do not have first hand experience with this, but there are threads on it).
Of course, you would miss pretty much all night time shows with this plan, so it doesn’t work if Illuminations is a deal breaker and/or if EPCOT is your absolute favorite and you want to spend the lion’s share of time there. But it might work so you could experience Pandora at night, hopefully with a slightly smaller crowd than if you went first thing. And you could have dinner at Sauli Canteen.
A long, busy day – but a fun one too!