Not to be offensive or anything, but the chances are good that all of you already have parasites. See the cayenne pepper challenge test in the link below, for example, to uncover tapeworms.
It's hard to answer your question. You want prevention and probably need treatment. Treatment causes die off, unpleasant but needed reactions that wouldn't exactly help with a fun vacation.
Maybe someone else will have some ideas. For sure it wouldn't hurt to take (best to make your own if you have distilled water available - see Utopia-Silver
for the little machine, or look elsewhere) some Colloidal Silver
(kills eggs), cayenne pepper, diatomaceous earth (food grade Pharmaguard on ebay) and (experiment to see if it causes die off or not) a Black-Walnut
/wormwood tincture such as can be found at Vitacost or Swansons, etc.
The cayenne pepper and DE will not cause side effects. Some activated charcoal won't hurt. If you get diahhrea, Wormwood
tincture can help combat & kill stomach & inestinal bugs - but use with care & read up on it.
says everyone she ever lab tested had Tapeworms
& everyone had other kinds of parasites
What helped me in case any of it can help you: