My son graduated a year ago this month.Be prepared for RAIN, too! We were washed out of the parade before commissioning and walking through puddles about 6 inches deep from a sudden thunderstorm at 8:30 am. The actual ceremony in the chapel is comfortably air conditioned. Ldies wore dresses and shoes that got VERY wet! Some had on dressy pant suits. The ensigns are in DRESS uniforms, so use that as a key. My son's fiancee wore dressy pants.
BTW, it's a LOT of fun. We stayed at the Navy lodge (very reasonable and right close by). Your son/daughter can get you a reservation there.
Congrats- now we're waiting for the winging (in 15-18 months- jets!). We hear that's quite a party.