You can find a list of suggested Scouting frequencies at http://k2bsa.wstearns.com/scout-frequencies/ and the same listing at http://www.scouting.org/jota/operators_guides.aspx
Note that these are suggestions. Crowded conditions, including contests, will no doubt require that you move a few kHz plus or minus.
Of particular concern are potential conflicts with emergency response traffic in the Caribbean. The ARRL has issued a note about traffic on 14.265 MHz as well as another note regarding Hurricane Nate traffic on 3.752 MHz, 7.242 MHz, and 14.302 MHz. In general, you should steer clear of any net traffic that you run across.
George Sparling, N2BEF, also brought to our attention a conflict with PSK and the new WSJT-X mode FT8 on 18.100 MHz. Both are recommending the same frequency which could generate interference. Since FT8 is the predominant activity at 18.1 MHz right now, we suggest looking for PSK contacts plus or minus 3 kHz. The frequency allocation for the 17 meter band runs from 18.068 to 18.110 MHz for CW, RTTY/Data modes.
We've also reviewed the currently recommended FT8 frequencies on the other HF bands and haven't found any other conflicts. We'll note that the K2BSA Jamboree operation used FT8 and found it at least provided examples of amateur radio contacts for Scouts. It's not a Scout-to-Scout conversation mode like PSK, SSB, and others. But it could serve as a useful demonstration of amateur radio capabilities.
As always, a Scout is friendly and courteous. Follow the Scout Law as you navigate the amateur radio bands during JOTA-JOTI weekend.