My first trip to WDW was with friends who had been once before. They had stayed on site and had a good idea of things to do etc. However we all sat down together, did some research together with them suggesting a few ideas and us suggesting a few things as well. Then we decided which days were best to go to which parks, what DH and I wanted to do, what they wanted to do. Then we would do the things we all wanted to do first, then maybe get some fastpasses we all wanted for later, split up for a bit and then met up later again to do more rides or meet back up at the room.
We have been on a few more Disney trips with them since to WDW and DLP and we have found this works. We will probably do this for the trip to DL which we will be going on together as well.
Seen as they have not been before maybe suggest some things that they might like to do, give them some websites/guide books to look at to see if there is anything they particularly want to do and then go from there.