Some of the information is a bit jumbled, but still accurate.

I recommend buying battlechests. Worry about Wrath when you get close to that. I did one set of accounts with trial accounts and one with battlechests and I like battlechests better. The trouble with trial accounts is it can be difficult to upgrade from a trial, to full to TBC in one day because of the Blizzard's billing system. I had to wait a few days to get my accounts upgraded because I was playiing 4 Draenei.

As for RAF, since you have a level 70 on your main account I would not include it in the RAF. This way you can use your main account to boost and get full XP. If account A (your main account) refers account B then you won't get the RAF bonus. What I would recommend is Buying 3 battlechests and referring accounts C & D from account B.

Now, if you are just going to level 4 toons from scratch and not boost you would refer from your main accounts.

You would get 1 free month from each account you refer.