Should I wear a Tankini or Bikini?

tomorrow's my friends birthday party and i think all of the girls are going to wear a bikini, there are a few guy going too. if i don't wear a bikini it would be kinda weird. personally if you look at me from the outside i don't look fat at all but my stomach is kinda fat. If i stand up my stomach would look fine but when i sit down my stomach will overlap. the worst thing is we're eating first then swimming so my stomach is gonna be bulged out and stuff... what should i do? D: btw about 3 of my friends have packs.