I agree with Sean. I think for outdoors radio activated speed lights with umbrellas will be easiest but you will need to recruit some help to move these around. I have a pocket wizard mini TT1 and some of the TT5 units. They work very well. Make sure to bring or purchase on site a load of AA batteries.

If you decide to go with monolights/strobes I can recommend the Einstein units from Paul C Buff which are very nice, very powerful and you can get umbrellas, battery packs and radio triggers that work with Pocket wizards. They can also be slaved optically to your on camera flash except then any flash will set them off. You Could easily put two of these lights with batteries, cords, chargers and small umbrellas in large suitcase.

Since you are on a beach maybe bring some sandbag type light stand weights too....

http://www.bhphotovideo.com/c/buy/Sa...3/N/4062040365