Pack them in your carry on, and schedule a private inspection with the TSA. That will prevent any loud mouth XRAY tech from announcing to the world you are carrying coins, and the coins will not leave your possession while they are being inspected. I'm not sure if you would talk to the TSA to arrange this, or the airline you are traveling on but I know it is possible.
Make sure you hand carry as carry on luggage. Most of the time, because coins look pretty odd in the X-Ray, they will need to check further. When they go to open bag, just request a private inspection and they will do their examination in a private room.
Agreed , private inspection is your right and the best way to handle it . Tell no one what you do and never ever let your bag out of your sight . When I buy in Europe I often have packages sent insured rather than carry them home .