Should i just let my kittens roam free around the house??URGENT?

We got 2, 10 week old kittens last week. Since then they have been living in their own room complete with bed, toys, scratchpost, litterbox, etc and have been getting on swimmingly in there. Now i think they are getting a bit bored of it as it is very small, should i let them roam about our very, very, very big (mive ) house? Im scared they will get lost or get out one of the many doors, or get squished by the feet of the many people, or fall of the decking of the upstairs which is like open plan and if they get outside we will never get them back as we live in open countryside. My mum says to let the in but i dont think she realises, what shall i do??