Ditto two4ruff...
You can buy Meclizine (exact same stuff as "Branded" Bonine, Draminine II) for much less money in quantity.
Walmart, Target and K-Mart all carry larger supply bottles. I recently purchased a 100-table (25 mg per tablet) bottle for $4 at K-mart.
Most adult meds are "not recommended for children under 12." Why??? - the FDA and drug makers don't test on study groups of children typically during drug trails, so have little statistics on the trails for those population groups.
Check your bottle of Tylenol, Ibuprophen, Sudaphed, etc. All will have this warning, yet there are "children's" versions of these over the counter meds, just in lower dosage.
Our pediatrician, and my brother who is a family practice doctor said there should be no problem with Meclizine for children under 12, just reduce the dosage. They said for a 75 pound child, a 1/2 tablet (10 mg) daily should do. However, consult your physician and try well before you sail so you have chance to discover side-effects if any.