More room is always better as long as they have an area where they can warm up. Until feathered Chicks can only regulate their body temperature by moving to a warmer area or huddling together. Sounds like you made the right decision. Mine only needed the heatlamp for about 3 weeks and wanted it...
The play gets a lot rougher when they start setting the pecking order at about 3 weeks. They usually won't actually hurt each other but they get pretty rough and tumble. I would "stir" the shavings everyday when mine were in their brooder. The droppings will dry out faster and not smell as much...