As others have noted, I have two phones US and Chinese I fly with all the time everywhere.
As to new sealed in box going out of USA with TSA can't see a problem. I have yet to see anyone require phones to require separate screen. If anything they are always reminding us to put it with our x-rayed stuff, LOL. Tablets would be another matter, but phones not an issue.
You don't mention where you are taking them. Does the country you bring them in allow their import w/o taxes even as gifts, assuming you aren't bringing in for paying friends.