I'll be traveling in a party of 5, all family members, 4 adults and a 12 year old. Will hotels allow us to stay in a double room plus an extra cot? Someone told me double beds in Europe are not as big as in US hotels.
A double room means a room for two--one double bed. Finding a room with two double beds and room for a roll-away is going to be difficult. You can find western hotel chains, like Sheraton and Hilton and Holiday Inn, near major airports, but then you will probably be far from sites. Consider an apartment in the heart of whatever city you are planning to visit. You will save on transportation and save big on food, plus you'll live like a "temporary local." Rick Steves guidebooks always contain apartment recommendations, and you are sure to find someone on this board who has experience with a rental company.
Mel, Google for "boarding house" in the various cities. Especially when you're staying for more than three days they make plenty of sense.
Try Eurocheapo.com they have alot of larger rooms listed on their sight.
My family of 6 will be staying in various types of places. In big cities (London, Rome, Paris) we found apartments through the vrbo.com website. Some, but not all, require a stay of at least 1 week. In smaller places we found a combination of hostels with rooms for 6, some small pensiones with family rooms, and in a few places we just had to get either 2 triples or 3 doubles. I spent time just going through different guidebooks at the library and found places with bigger rooms.