The other option is just get them to a zone and quest, with the rested XPs it goes quick. Drive with the lowbies, pick up everyquest and then shift to the 90 for PWNage. Or find a grind spot and just sit there. I found when I ground it out that if my lowbies were trying to assist it seems like my non-90 shaman were getting more experience than if I just let my 90 tankadin get the glory. They also killed faster and that meant more XPs.