Great question OP. I have found myself with this issue in regard to Shadowfang in the next patch. I will need to acquire 2 news ones so that they are ilvl 25.
This was already stated- but you have a 50/50 chance of the items scaling to your twink or your main. You need to find out if you can do two SFK runs in the same time that your twink (and a group of 4 other twinks) can run SFK. With all of the RP, I do not think this is the case.
Few tips for farming SFK- guardian druids do an absurd amount of AOE damage. Queue with 2-3 twinks with frag belt- you can pull the whole instance in a few pulls. Arcane mages also do crazy AOE.
Good luck farming!