If you are going to go with 3 gallon batches you can get a 5 gallon food grade pail and ferment in that also. That way you'll have plenty of headspace for krausen. I'm not positive, but I think the 5 gallon pails at the big box stores are all food grade.
Something is always fermenting....
"It's Bahl Hornin'"
Kegged: Bourbon Barrel Imperial Stout
On Deck: German Lager