Just a couple comments...
- You say you land at 4:30 pm. I'm assuming since you say you will have a car, you are not using DME? Even if that is the case, you will probably not arrive at POR until 6ish. Check in, catch a bus, you could be at the MK about 7:00. But what if your flight is delayed? What time do you have to leave home in the morning? We much prefer exploring the resort and maybe an evening at Disney Springs on arrival day. From POR it's a lovely boat ride!
- Have you ever been to AK? Give it a chance, we love it. The theming and attention to detail in the design is brilliant, the food is very good, and the two best musical shows on property are there. I hope you like it!
- Don't stress too much; you're already ahead of the game with the planning you are doing. Have fun!
These were two of my first thoughts as well. Driving from the airport may also be your only chance to eat outside of Disney for a while (without losing precious park time). Between jetlag and rough travel we often take the first day to do non-park things such as DS, Hoop Dee Do review, Jellyrolls, or exploring the resort so we don't waste time later.
We always park hop, but we go at least once a year. AK gets a bad rap for being just a half day park, but there is much more than KS & Everest. If you get a chance search youtube.
HS on the other hand is something you might do in 1/2 a day. I try to split HS and Epcot twice, breaking Epcot into future world one day, and world showcase another. Three FP+ at HS, then eat and drink around the world. Remember even if Epcot opens at 8:00, world showcase does not open until 11 or 12.
Ropedrop at MK is something of an event, but consider getting an ADR before the parks open. Tusker House at AK and Crystal Palace at MK take ADRs before the park opens. This means you get great photos on your way to breakfast, then you're in the middle of the parks when everyone else is at the front for rope drop. (being you are talking about May, these may already be booked)
Even with having a car, look into Disney transportation. You can get from MK to Epcot faster on the monorail than walking to your car and driving. Same with Epcot and HS on the Friendships from the international gateway. The downside is getting back to your resort for breaks. I personally resort hop if we're not staying at a monorail or crescent lake resort. Wildreness lodge is a great place to relax in giant chairs for an hour, or lounge at the pool at GF.
Always remember no one way is right for everyone. Try to be flexible when you can. If you have any questions feel free to ask.