Using the JZ calculator
(assuming you are doing 5 gallons) I am getting 2 packets of dry yeast needed. (don't forget to rehydrate using the proscribed method).
I agree also on the champagne yeast, if you use that you will get no flavor out of it and end up with a dry, tasteless beer. Also, pitching after fermentation does not work (from experience.) You will just end up with a bunch more dead yeast on the bottom of your fermenter.
And as for sucrose, what happens is that as yeast metabolize it, they soon stop producing the enzymes needed to metabolize maltose after 1 or 2 generations, meaning they will be unable to finish out your beer...
I am assuming though that since you are doing a barleywine there won't be much if any sucrose in your recipe.