If you just want to replace the stationary showerhead with a handheld, the type of rough-in valve won't matter. But if you want both - to add a handheld in addition to the main showerhead - it is another story (valves, diverters, additional pipes, etc as already mentioned). Since the plumbers have done the rough-in, use the handles your ordered for them and get any handheld shower head from HD. It'll work fine. I've done it many times before (replaced mine again last week - and I have 50+ yr old fixtures). All you would be doing is unscrewing the main showerhead and screwing a new one onto the pipe that extends from the wall.

I only have one handheld in my house, it's a Grohe Relaxa Top4 shower head: I'm not trying to sell you on this particular head, but I'll tell you why I bought it; as an option, I could buy a 40" long slide bar instead of the more typical 24" bar. I have my bar from 46" to 86" which puts the head between 53" and 90" above the tile. My shower has an 8' ceiling. If you can find a longer bar in the Delta line, you could consider a similar set-up. Here's what I recommend: I agree with your plumber. I think two valves or a valve/diverter feeding two heads on the short wall of a tub surround shower is overkill. I'd install a shower on a vertical slide bar. Again, I only have experience with the Grohe Relaxa set-up, but it's been in for maybe 15 years and the head still easily slides up and down, the bracket that holds the head is rotatable...but it never droops. There are no leaks or errant sprays of water that leak out of any of the fittings. For your potential seven footer? If he does indeed grow and you want the shower head at a higher height than you can get with a typical slide bar, spend $20 or $50 or whatever they cost, and buy a shower head wall bracket: You can install that bracket as high up on the wall as you chose, and when your tall son takes a shower he can take the shower head out of the sliding bracket and install it on that high bracket. When you build the shower, install a horizontal piece of 2-by-6 backer between two studs at the height you think you'd like the bracket to be. When you go to install the bracket, drill on a grout line and you can secure the bracket onto the 2-by-6. I'm not trying to talk you out of what you want to do. If you really want to do it, fine. Not that I typically hand out parental advice...but don't make the shower too comfortable of a place for your teenage kids. You want them in and out instead of taking 30-minute showers. lol Regarding trim versus valve and cartridges? The valve body is the rough-in brass body that will contain what goes behind the wall. The cartridge is included with the valve. The valve trim is usually just the bright shiny chrome part that people ooh and ahh over. In this day of specialized valves and trim kits, do make sure you match up the valve with the trim so they are compatible. FWIW, I have thermostatic and pressure-balanced valves in my house. I notice no difference at all in water pressure or temperature control between them. Good luck!

Isnt that silly? I have no idea why they include a cupcake soap and forgot to ask my husband it it really came with it. I am 5'2" - probably not as short as your DD"s :) But not to tall either. Oh and we took out the water saving disk. I think some of the reviews people didnt do that. They make it easy to take out but in there so it complies with laws I think. I dont take a long shower either and is actually shorter now that I have a good showerhead to rinse my hair quickly.

You probably can mix and match components from different vendors; once a pipe leaves a fixture, valve, etc., the next item in the piping doesn't care what was before it.