Hi Jonathan:
Well, you either have one major project with 3 sub-projects, or you have 3 projects.  My question is: "is book xxxxx" a next action?  Can you go online or call a travel agent and spell out exactly what you want?  If not, what do you have to do first? - choose dates, fix budget, research flight availability / prices?  The book has some very good examples of working backwards until you have something concrete that you can actually do now.
Recently, I had to take an emergency business trip.  The first thing to do was to call the airline and make a reservation.  I decided that the next thing was to pack, then dash to the airport and on to the plane.  Once I was in my seat, knowing what plane I was on and my arrival time, I whipped out my cellphone and made car and hotel reservations.  That was the most logical order for that little project - unless I knew what plane I was on, other arrangements would still be up in the air (even if I was not).
My experience is that once you start on a next action (something fairly mechanical - a gimme, or easy win), it becomes easier to figure out what should come next - so do it right away or bookmark it for later as the next next action.  Micro planning does not necessarily all pan out - the big picture and the next action are all you really need - and sub-projects if the big picture is too big.
Andrew