I had a 4d scan a couple of weeks ago (we already knew we were team blue) and we were asked almost straight away if we knew, the sonographer was flicking past things really quick and unless you knew what part of the body she was looking at I don't think you'd see. She then said he'd flashed at her, but I think if we didn't want to know she'd have been able to avoid it. She took measurements first, again quite quickly of head, tummy and legs to check all was well. This all looked like a normal scan does, then she focussed on his face and flicked to the 4d images. It was brilliant, but as I say I think you will both be ok with not finding out the sex of your babies.
Ooh sorry went on a bit, does sound like braxton hicks, but not long to go for you hun - i bet you're sooo excited now xx