Teen bikini fashion blunder, how would you had solved it?

Here is the deal, last summer you have a BBQ/pool party, with a mix of boys and girls of all ages and their folks. A woman you know but not real well, but well enough to invite shows up fashionably late as is her usual with her 13yr and 16yr old girls in tow, the 13yr old is wearing a very small Rio bikini a two-piece if you haven’t figured, and the 16yr old in a black thong singlet. As one can guess most of the boys gravitate to them like ants on a pin nic hotdog. The girls were not being flirtatious but their swimwear made them a hit. Some of the other girls whom I suspect has sights on some of the boys complained about it because the boys they wanted the attention from were not giving them any play. Then the great debate runs wild, should the girls be asked to leave, cover up or should the boys be told to cool their jets? If there was no dress code stipulated in the invitation even if the girl’s mother did not feel or think to dress them more conservative does it fall on them because of the fashion faux pa? Should they get a pass this time and have a dress code in the invitation next time? Because there are young kids should they be told in order to stay cover up, change or leave? What is your thought on it?