MONTAUK for the day ?

I figured Im sure there are going to be at least a handful of you that are Montauk connoiseurs and can tell me what to do there for the day. It will be me, hubby and the baby.
I was thinking a lunch cruise, something on the water, maybe some walking around, any aquarium, museums, etc. anything 'too see' (the lighthouse?).

Give me pointers girlies!

I plan to go (unless I change my mind ) this coming Friday and coming back in the evening, hoping to avoid traffic both ways! Im SURE (I hope ) I shouldnt hit ANY traffic coming back west in the evening...)

So 27 goes straight to Montauk, where to go at then end of 27 ? Tell me as if youre telling a tourist