1st 10 gallon all grain yeast starter help?

Hi all, this is probably a simple question, buuut...

Im doing my 1st 10 gallon batch, recipe calls for 2 vials of yeast. I understand this is to get enough cells into the extra volume over a 5 gallon batch, but how do I handle the starter sequence for this?

Make a starter with both vials in it and pitch that?
Make a starter with one vial in it and step it up?
Make a starter with both vials and step it up?

Thanks in advance. ideas of amounts for the starters would be helpful as well.

Generally you just use 1 vial of yeast to make a starter. Just make the final volume as per mrmalty

Thanks,

Mrmalty says 4 liters with both vials, using only one vial I would need 12 litres!

Even if I step this up I am getting the feeling one isnt enough so ATM im planning on a 2L starter with both vials. (I have them right?) and then a step tomorrow to 4L

Unless someone tells me I'm completely crazy...

Also conceived pitching one vial into started and then adding second at step up or at pitching. Not sure if this would work either.

Please forgive the noobness, just slightly outside my comfort zone