Yes, you can place one order for three crosses, and select engraving. Once you have selected your crosses, you will find a pull down menu. It will ask if you would like engraving. Select yes, and put your three neames in the box. If you cant fit them, you could put a note in the customer shipping notes.
The best way to do this is to place ONE ORDER, but add 1 cross to the shopping cart at a time. Enter the engraving info for the first cross and press add to cart. Repeat the procedure for the other crosses.