Your coach would not be asking you to try the skills if he/she didn't think you were ready. But giants are certainly a very scary skill the first time around. Since you've got multiple spotters, don't worry about the technique much on the first one. Keep your body in a tight handstand and let your spotters do most of the work. I closed my shoulders on my first giant, too, so for the next few I focused exclusively on keeping my body in a straight handstand position. This way you'll learn that you're going to make it over just fine. Even with using very little technique to get yourself over, your spotters will keep you safe. Sometimes that's what you've got to do to get over the fear. Then gradually start working on the correct tap and getting over using more of your own power as you gain confidence.
Good luck! Giants are a really fun skill once you do get them!