We usually arrive around noon on a Sunday and always spend a few hours at Epcot that evening. We grab lunch at the resort (AoA) when we arrive and then spend an hour or so getting settled in the room (we drive, so our luggage is with us when we arrive) and then head to Epcot. We love getting a head start on things by hitting a park for a few hours on arrival day. The extra $11 in ticket cost is well worth it in our eyes -- especially now that FP+ is available because we know we can get on at least 3 attractions. We do a few rides and then we have dinner somewhere and head back to the resort for a quick swim and then to get to bed at a decent time so we can hit the ground running in the morning. It works well for us.
That being said, I'm not sure what I would do if we weren't arriving at the resort until 5:30. It would probably depend on several things: ages of the kids; hours of the parks; what is planned for the next day. If the kids are able to stay up late without having meltdowns, I'd probably plan to spend a few hours at a park on your arrival evening. I'd choose the park with the latest hours -- most likely MK. If I planned to have a full day (meaning rope drop in the morning and staying until closing at night with a possible break in the afternoon) in the parks the next day, I would try to be back at my resort room no later than 10:00 on arrival day -- which would probably mean heading out of the park by about 9:00. In your situation, if everyone in your travel party is a tween or older and you think they can handle the long travel day, then go ahead and plan some FP's for that night. I'd choose MK and schedule 3 "must do" rides -- with the first one being scheduled from 7-8, then 8-9, and 9-10. I would plan on riding the last ride as close to 9:00 as you can. Then you can decide if you want to do some additional things stand-by or just head back to the resort. We've found that stand-by lines really start to decrease by 9:00 because everyone wants to go to the parade and then the fireworks. It's great to take advantage of those shorter lines at least one night at MK. If you want to see the nighttime parade and fireworks, you could plan those for a different night.
If you think that heading to a park on arrival night might be too much, then just plan to hang out at the resort and swim. Or take a bus to EP or MK and do the monorail loops before heading back to AoA. Or maybe plan a late dinner at a resort table service restaurant.