You'll feel 2 is not enough, then consider getting 3, then 4, and might as well get 5.

If you boost with a 70, you're better off inviting 3 more random people in your group. Group Bonus is that huge a difference.

2-Box with a lowbie and a 70 is a severe hit in xp gains without group bonus. Add 3 more, and you'll get more xp per kill.

Anyway, level 1-8 or even as high as 10 as 2 lowbies; then level 10+ you can boost and see your progress.