Well, you're looking at about a 4 week difference in age there - and given the weather that time of year your first batch will be ready to be up and out of the brooder at 4 weeks (imo) - which will open up the brooder space for your next batch. Even without the age disparity, the total brooder space that you would need to accommodate all the birds would be pretty limiting to combining them once they start to really take off in size.
I would brood the first batch, move them out, brood the second batch and then start doing intro/integration when the littles are big enough to start going out for field trips during the day by having them spend some time in sight of but separated from the bigger chicks.
