Hi Julie,
New to this myself, and as you can see my aunts family name is Doolin, my guess, would be Irish but if one of the other readers see your post, they will most likely be able to give you a proper answer.
If you recieve no more answers to this one, put a new post up saying 'help with roots of name Doolan please' and I'm sure someone will give you better help than me.
good Luck Eileen