No worries Amanda, I see everything. First of all, congratulations! You must be pretty stoked.
As for your lil' problem here, do not stress, this will be a breeze for you. I can sort of understand wanting to cover your tattoos for this event since they are "somewhat conservative," but if they saw your tattoos would they not give you the money in the middle of the luncheon? Probably not. So while you shouldn't show up in a spaghetti strap tank top and hot pants, you have a bit more leeway than you think.
A simple combo of a breezy blouse and narrow trousers will be your best friend. I know you said it was hot where you live, but when it comes to leg covering, pants are a hell of a lot more comfortable than tights. I think these pants look dressy without being stuffy and you can even roll them up once or twice to above your ankle. Since it's a luncheon maybe you can have a bit more fun with the top you wear, like a semi-sheer top (worn over a cami, of course) that will be modest but still remain fun. Even if your tattoos are visible through the fabric, it's no biggie because it won't be super obvious and let's face it, no one can really come up to you and ask "what's under there?"
Another option is to wear a sleeveless shirt with a lightweight cardigan over it. This way you won't have to bake in the sun in the events preceding your luncheon, but once you get there you are professional to the max. I love the linen cardigan because it will be super lightweight, almost like wearing nothing at all!
Dolce Vita Rosetta Suede Round Pump $165, Saks Fifth Avenue
As for shoes, keep it simple and comfortable. I think you can get away with pretty much anything, a pair of nice pumps (no platform!), classic oxfords, or even ballet flats. If you wear sandals, make sure your feet get a pedicure--either from a salon or DIY. Nicely painted toes DO make a huge difference!
So go on girl and get.that.money!
Have a fashion conundrum? Let me at it! Send me all your queries to firstname.lastname@example.org.