Taxi will be the most efficient way. There won't be an efficient way to get there via Disney Transport, especially early enough in the morning to get them to WL and then have all of you get to MK before it opens.
I suppose the ONLY way via Disney Transport will be bus from ASMu to MK, and then motor launch (boat) from MK to WL. However, I have no idea how early those boats start running. I can tell you that before the park opens, there will not be buses FROM MK back to any of the resorts ... there's no need for such service.
If they take the above route ... buses run about every 20 minutes. So if they just miss a MK bus, they'll have to wait 20 minutes, and then a 15 minute bus ride. A 2 minute walk to the dock, up to a 20 minute wait there, then maybe it's a 10 minute ride on the boat. If they have to get off the boat and meet you somewhere, I don't know how long that will take. But then you all will wait up to 20 minutes for another boat, then a 10-15 minute ride to MK. So not including downtime at WL, they are looking at being on and waiting for Disney Transport for up to a total of 102 minutes, one hour and 42 minutes PLUS any time they spend at WL with you. All of that in the early morning BEFORE an early start to a theme park day.
Yuk.
A taxi is looking better and better. Immediately available, and probably about $15 or $20 tops.
Do they need to meet you at WL? Can they just meet you outside MK? It will be much much MUCH easier for them. They can just take a free Disney Transport bus from their resort to MK. At the very least, that will save them more than one hour that morning.
