I think they are separate. We had one in the 3-4 and one in the 5-7 and I don't think they ever did anything together. In the evening when we went to pick them up (usually between 10 and 11pm), the little ones were laying on mats with the lights turned down watching a movie (or sleeping as the case may be) and the 5-7's were in the back room area doing playtime, computers, dress-up, etc.
I always had to drag my 6 1/2 year old out of there!!