Seeking accomodations for 6 near olympic park

I am looking to visit london for the first time with my wife, 1.5 yr old son, and my brothers and sister, for a total of 6. We just need a place to rest for the night, as we plan to explore the olympics and london during the 2 weeks. Ideally it would be at least 2 bedrooms, with at least 2 full size beds and one twin. We don't plan on renting a car or anything, so something close to public transportation. Thanks!