We still rarely wash DDs hair and she'll be 4 in June. We rinse with water but only wash if it's actually dirty,like when she gets her dinner in it, or sand. During swimming term I put conditioner in it on those days.

She had similar hair to what you describe when she was your DDs age, I just gave it a bit of a brush if it was knotty, that was all it needed. It was only really fluffy if I'd washed it, otherwise it was just curly.