First of all, my highest regards for stepping up and deciding to compete. You have a great mindset and it takes a lot of character to get on that stage.
I have a couple tattoos, one small design on my inner bicep and a large (almost billboard) across my back. Both only black. Almost all bodybuilders these days have tatoos so don't feel singled out. From my experience and from what Ive seen theres almost no way to hide them. Just tan really really dark. That's how Dorian Yates hid his forearm.
It's tough because you have a LOT. All said and done, just do it. I can't really suggest any products to you because most of the stage makeup people use isnt designed to go with a spray tan. Just tan dark as hell.