This varies greatly between different companies. It's very important that you understand how much of your payment could be lost due to a cancellation if you do not have travel insurance. All tour companies and cruise lines will offer you some kind of travel insurance policy. The most important feature of those policies is one that protects you against losing the money that you paid in advance for your trip if you are prevented from traveling due to sickness or accident and certain other covered reasons. Some of these policies also provide some coverage for medical expenses that may be incurred during the trip.
Credit cards are widely acceptable in Europe at restaurants, hotels, gift shops and gas stations.
ATMs are very popular in European cities. Just take 1 wheeled bag, one that you personally are willing to tote around. Being weighed down with too much luggage WILL diminish your travel experience, even if you're on a guided tour and your bags are handled for you much of the time. If you insist on taking more than one piece of luggage per person, you should not travel by rail, where the extra bags will prove more of an inconvenience than when traveling by car or motorcoach. Unless you really want summer heat, the best times for southern Europe are May and October.