Flights to the United States from Dublin or Shannon are pre-cleared in Ireland. United States Customs & Immigration operate at those two airports and you legally enter the United States before you get on the plane in Ireland. When the plane lands in the U.S., it can go to a domestic flight gate and there are no further formalities here.
BobK/Orlando
Indeed.
I'm one of those many international guests regularly dropping into WDW. Actually these days fly Aer Lingus (Irish airline) that connects through at DUB.
Preclearing is a great thing! After that you will arrive at MCO as a domestic flight. But if they haven't considered it; they are doing wise to make sure to leave enough time arriving in time at the airport to go through preclearance. It helps a lot if they are departing from said airport instead of connecting through but sometimes it can take a bit longer if something needs a bit of an extra check up or you need to wait for something. Have to say though; the atmosphere there is totally different than clearing at any US airport within the US. A lot less work pressure for sure makes a big change.
As far as DME goes; Disney no longer sends the DME labels overseas. So no choice of having DME use those to automatically have your luggage picked out and delivered. If desired your family can hand in the baggage stubs the airline gave them and DME will use those to track down the bags and it will proceed as you are used to as US guests. However because of not being able to use the DME tags it can add quite some time (to give you an idea, back in 2009 when we still could use the tags, we had 4 suitcases labeled and delivered to our room about 5 minutes after getting there, the 5th non labeled suitcase would not show up until 3 hours later, big downer when you check in around midnight).
The other option is to collect their luggage themselves and proceed to DME check in and take the luggage on the bus with themselves. I've been doing that ever since no more tags for us overseas and it's by far the quickest option. Asking, begging, whatever, nothing helps. Tags will not be send overseas.
Obviously you need to check flight info with them, but that's more to give DME an idea of when to expect them than them actually being scheduled on a specific bus. I'm putting my money on them flying IE (Aer Lingus), which would have them arriving at 5 pm on the EI120. It's one of the direct flights, IE is relatively cheap (dirt cheap if flying business class) and has a good product.
The arrival time and domestic clearance does add up for time being saved. Last year I was at the YC about 1 hour 40 minutes after the jetway got connected to the plane. And that is considering I am the last passenger to leave the plane (need assistance, so first on last off), use up more time getting my powerchair from travelsafe to use mode and DME actually having to wait some time for a bus with lift. Wasn't even the first resort to be dropped of either.
Oh and if booking DME for them; give them the heads up that DME will schedule all for a departure of 3 hours before flight departure time. Including those guests on international flights. Best thing to do is call DME on the day before check out when getting the DME-letter and having them move it up to 4 hours prior to departure (so if flying EI it would become a pick up at 4 pm for the 7 pm flight). The number is in the letter and when calling and saying international travel, most will not even let you finish and already suggest moving the pick up time to an earlier one. Most of the times it's not that much needed, but if the ride to the airport takes longer and it takes longer than normal to go through customs it can easily add up.