The first step is to solicit host families and see how many beds they have as well as what pets. This way you can match people up with fewer problems.
US Sailing recommends that for junior or youth events, you segregate by gender, regardless of the team makeup. Co-ed teams will have plenty of time to talk while at the venue and on their way to and from the race course.
See if your state requires criminal background checks for adults working with minors in a volunteer capacity. This can apply to host family housing, but requirements vary from state to state.
It's a nice idea to have all the host families meet a night or two before the regatta. At this meeting, you can let people know who is staying with them, review transportation plans and the event schedule. You can also send a letter to the host families if you prefer.
Clicking on the hyperlinks above will enable you to download templates to use for your championship.