Consult your pediatrician. Dosing with Lactaid or similar enzyme products is generally driven by individual response. Some need more than others. However, taking a replacement enzyme which will help the little one tolerate milk & milk products may be more efficient than trying only find lactose free products.

This is from MEDSCAPE Reference - which I find to be a reliable source - http://emedicine.medscape.com/article/930971-treatment

Lactase derived from yeast can be added to milk products as drops or ingested as chewable tablets prior to ingestion of lactose-containing substances. Studies demonstrate varying success. Digestive supplementations are apparently limited in their ability to digest large quantities of lactose.
Yogurt with live cultures is generally well tolerated by individuals with lactose intolerance. Dairy products with reduced or no lactose are widely available.
The risks of drastically limiting or excluding all dairy products in populations such as blacks, who may be at risk for nutritional deficiencies, have been illustrated.[8] The importance of maintaining a good intake of dairy products in the face of lactose intolerance has been stressed.[8]

Hope your vacay is great! and tummy trouble free! PEACE