If you're running 5 toons with the new XP bonus, you've got a few options. If any of your toons are not XP bonus they are gonna get left behind bigtime in levels.

I'd recommend figuing out how few starting areas you can begin with depending on your class choices and level them up to about lvl 10 or so there. I've heard plenty of reports of people pulling 1-10 in about 1 hour 15 minutes. At this point you should be near enough larger cities that being near class trainers shouldn't be a huge deal, along with the fact that since you'll still be running quests that are designed to be solo'd who cares if you are training all your new abilites becaue the mobs are going to die fast anyways. At lvl 15, head to town, buy your new abilities, do any class quests you may have passed by (oops) and start yourself instance grinding. In fact I'm about to go check the XP post and see if people have posted numbers yet on what kind of XP they are getting doing non-boosted instance runs with the XP bonus.