I have a friend who showed to me the same cake design you have on the pic for her birthday cake! it seems to be a very popular design. She wanted to have the glitter shiny effect also; but in silver. It is hard to achieve that kind of glitter and be safe at the same time to eat since the glitter or metallic colors that are very vibrant are not meant to be consumed….having said that maybe you should explain this to your client? that way, your client would be ok with a no too shiny effect but close to it :-) you can go an edible but less glittery way to do this or change a bit the glitter part of the design. You can give to your client some ideas such as using spots (instead of all glitter gold in the bottom tier) of gold leaf (a bit expensive but you would use just spots here and there, or use round sprinkles ( for the sequins ) glue them on to the bottom tier and spay them with gold (Wilton and other brands have this) , or gold luster dust with pearl dust combined and use an airbrush???? hope it helps
kleiza rojas fitzgerald