Ok earlier, I asked about diverter valves and ballanger said I should look into putting in separate mixers for a shower head and an overhead rain head. I understand how that would work out better than installing a diverter. My question now is this:
The shower we are taking out was not original to the house. It looks like they tied it into the sink water supply with 1/2" copper piping. Should I go ahead and keep these connections to add the two new heads, or should I tap off from the main line which is 3/4" ? The main lines are actually closer to the new shower than the sink is, and I am mostly concerned with maintaining good water pressure. We are having a plumber install this for us, I'm just trying to be an informed consumer so that in the end we are happy with the work. He says it doesn't matter which way we do it. Thanks in advance for your expertise!

My question now is this:
The shower we are taking out was not original to the house. It looks like they tied it into the sink water supply with 1/2" copper piping. Should I go ahead and keep these connections to add the two new heads, or should I tap off from the main line which is 3/4" ? The main lines are actually closer to the new shower than the sink is, and I am mostly concerned
I would take off from the 3/4 " mains. Leaving the 1/2" branches would mean a loss of pressure to the shower every time the lavatory made a draw. Good luck, Tom

Tnt, I wondered where you went. Do you know that you don't have to open a new post and you can just keep talking back and forth on the old post? Anyway, Tom and I agree regarding the 1/2" tap being too small for piping two shower heads in series. I am concerned that you plumber said,"He says it doesn't matter which way we do it. Thanks in advance for your expertise!" I think it certaining does matter. You can't get the needed volume of water to run two heads. Start looking over his shoulder or ask to see his license.