No worries, we are not skinny girls either! I do wear a bathing suit, just cause I dont care :). Ii typically get Speedos from a sports store in Colorado that has them up to size 26 - great styles and they really hold up. or, this time of year, Sams has them for 1/3 the price up to size 18.
My partner prefers to wear mens bathing suit shorts - she too is (IMHO) lovely and femine, but likes that she can go to the ladies room without completely undressing. We both wore them when in Hawaii last year as it was cooler and the zip pockets are great. integrated underwear - how wonderful!
On top she either wears a rash guard shirt (rashguard.com), or the top of what they now call a tankini - a bathing suit top that stops at your waist or hips or even below, depending on the style. Those we get on line - Lands End has some really nice ones with matching shorts and there is another catalogue we order from with sizes up to 5x. Cant remember the name. their stuff is not as nice, but loaads of choices.
Ii like the rash guard shirts when snorkeling rather than a tee as it dries fast, doesnt weigh me down and is wonderful in the water. they run quite small tho. Dive shops all have them too.
I am SO SO excited about the trip! Come and join us.
Becky