You can wear whatever you like at the Tiki Bar. It is a very casual OUTDOOR place with a beach vibe. That time of year weather can be unpredictable but typically warm enough for shorts and a tee shirts.A light jacket may make things more comfortable.
The Tiki Bar menu has a variety of options for food -- a long list of appetizers from fried pickles to raw oysters to cheesesteak egg rolls. They have list of main courses dishes including salmon and luau beef skewers, with handhelds like rockfish or Mahi tacos to the basic cheeseburger. Pleas see the menu at the link below. http://www.tikibarsolomons.com/food-menu/
Relax and enjoy a leisurely one-hour sightseeing cruise on the river. You will sail the busy Solomons inner harbor, see Solomons Island and the Chesapeake Biological Laboratory, pass underneath the Governor Thomas Johnson Bridge, and turn back at Pt. Patience and the Naval Recreation Center.
Upon arrival, check in at the Calvert Marine Museum Admissions Desk and pick up your boarding pass(es) 15-20 minutes prior to the public cruise. You will need to exchange your complimentary gift pass for a boarding pass. A ticket purchase and boarding pass is required for each person, including infants, to board the Tennison.