Last year DH, DS(3) and I went as scarecrows and our 8mo old was our little pumpkin. I made the costumes with short sleeves and such for the heat and other than all the hay (raffia) attached to our pants and such, were normal clothes.
This year we're doing a Pinocchio theme - my 4 year old will be Pinocchio, my now 1 year old will be Jiminy Cricket, DH Geppetto and I'll either be the blue fairy or Figaro. I plan to make our costumes again so I can alter them to work for the sept heat!
I Don't think these would really count as not very costume-y though I will say it was so, so much fun dressing up. DH thought we were going to feel a little silly at first but in the end had a blast!