It's great having friends and family stay over especially during busy times like Christmas. It's not so great if you've got to make them all sleep on the floor . There are a few ways around this problem.
Get a bigger house with at least 3 extra bedrooms. It sohuld only cost you extra tens of thousands. It also might take a bit longer than nipping to IKEA. If that's not an option here are some alternatives to beds and mattresses.
Sofa beds are an ideal solution. They can act as part of the normal furniture then transform to fulfill your guests sleep needs. The bonus with sofa beds is that they are not very different to sleeping in a bed. They're pretty compfy and they are easy to get in and out of. Sofa beds can be bought as part of a suite or own their own so you could even stick one in the kitchen.
Air mattresses are pretty useful too. They give a fairly comfortable nights sleep and its easy to keep a handful lying around. They do have to be inflated though which can be an added stress. Provided you have enough floor space air matttresses can provide you with lots of extra beds.
For the true sleep adventurer there's hammocks. You've got to have somewhere to hang them but if you do they're great fun. Probably a better idea for the younger visitors as they can be tough to get in and out of for older relatives. Then again there's always flooring. The chances are you're visitors won't be in a rush to return though.