Add Wireless Mouse+Keyboard to existing order?

I ordered a Mac mini a few weeks ago. It's stated to ship on 3/4 (can't wait).

But when I ordered, I decided not to include the wireless keyboard and mouse. But now I'm thinking, maybe I do want them... And it's cheaper to get them both with a machine rather than after the fact. Now I'm wondering, could I add a mouse and a keyboard to my order? My main concern is will it mess with my precious shipping date? I don't want to add them, then see my shipping date move back to 4/1 or something!