The safest route will be to have all of your accounts in your name.

If three of the accounts are in your name, and two are not, ideally (painfully, I know) you will want to make those two toons over again.

By purchasing a 4th and 5th accounts, and RAFing from the 4th to the 5th, you will have two toons which can level from 1st to 60th very quickly.

You can use your existing Paladin (not in your name), in instances to boost with. If the toon is half geared, you will boost very quickly.

Something like: Deadmines -> Stockades -> Scarlet Monastery -> ZF/Sunken Temple -> BRD -> Ramparts -> Underbog.

70 to 80 will be a lot less painful with only two toons doing collections.
Regearing two toons would be a process, but in the end you have toons which are indisputably yours.
Your other toons being comparatively very geared, will help out enormously in heroics and such.

Also, with five level 80's at your disposal, dailies can help to AH Purchase ups especially for your tank.
A few titansteel pieces, along with a decent weapon, some AH Naxx/Ulduar stuff, and you'll be on your way.
I'm actually gearing a pally tank like this now, but its my first team at 80.
I went Enchanting and Skinning, but am thinking of switching to Tailoring for the 2nd profession.
Enchanting because none of the others had it, and I'd like to be able to DE instance drops.
Tailoring for the extra cloth to sell, but the cloak enchant looks to be an ok bonus too.

Bottom line, you'll not want the chance to lose all 5 accounts, for using accounts which are not yours.