Boy Scouts and expert shoppers are alike in one very important way. Make a note of those important bits of information on the family's shoes and clothing sizes. Make sure they are in European, US and UK sizes. Look for bargains in your destination's daily newspapers. Check if sales are in the same area so that you can spend more time shopping and less time travelling between shops.
Shoes are an important part of shopping.
Wear the most comfortable ones. Your will be able to try on the clothes straight off the rack. A bag for all your goodies is better than six or seven bags. As a traveller, credit cards are much better than cash. However cash can be convenient if the queues at the cash counters are long and if you want better bargaining power.