Looking at the map it looks like the Regency is just a little over a mile from DL, while the Hyatt Place is a little over 2 miles. It would be a better deal if the offers of free shuttle/breakfast were the other way around. Either way, if you look at the sheer difference in size between WDW and DL, either trek is doable and not adding a lot to the mileage you would have been walking at WDW. Although that is another matter entirely after you have been wandering around the DL resort all day. Don't forget about parking fees if you end up with a car

I know they've recently started the reserved viewing for Fantasmic at DL. You might want to check into those packages to be ensured you get a good spot. I like both the WDW and DL shows for their own special merits, but the use of the real Steamboat in DL definitely gives it that added little bit extra!
You should really be able to see everything at least once in a three day park hopper, especially since they should be having longer hours when you go. You might check around on pricing ~ I had a bit of sticker shock when we arrived at the parks and I was deciding on the amount of days and hoppers vs. non-hoppers. I think it ended up being too close to $1000 for the three of us to have park hoppers and a one day ticket for my brother that just joined us for the day to have lunch at Club 33. Me and my big mouth offering to pay for the tickets

but I wouldn't trade the time we were all able to spend together that day

The chance to see even some of the 60th stuff should be pretty cool
Biggest thing I always tell people that go to DL after having gone to WDW many times is you will be so pleasantly surprised by how much easier it is to get around DL ~ smaller parks by far, even though DCA is pretty big once you are in it, it is nowhere near as much walking as any of the WDW parks.
FP and single rider lines for the win ~ especially FP for Radiator Springs Racers. We also lucked out with much shorter lines for that attraction late at night, right before World of Color was set to begin.
OH, one more thing I'm thinking of right off hand, it is hot there, but no humidity so it isn't as oppressive as Florida. I would move to Southern California in a heartbeat to be closer to DL for the better weather if it wasn't so darned expensive to live out there. Not that Florida is much better, but it seems more doable to me...plus WDW is so much bigger.
I'm so excited y'all are finally getting to go!!