If you have a main 70 that you want to use to "boost" the others then you DO NOT want it linked in any way shape or form to ANY of the other accounts. Here's why:

RAF bonus only applies to toons who are within 4 levels of each other for the tripxp. If any are linked to your 70 account and you use the 70 to boost since he is much higher than the rest they wont get the tripxp bonus from killing mobs.

What you would want to do is start a totally new account. Have account A refer account B. At this point you can either have them all chain refer or just refer all from account A.

A refers B, C, & D or A refers B, B refers C, and C refers D - All leaving account X(70 toon) out of the loop.