Don't worry too much yet! You are on the right track. If the egg was laid with a soft shell, or no shell, or a thin shell that cracked, it is totally normal for the chickens to eat the remains, and this won't make them egg eaters for life. Also an egg dropped by a new layer out on the ground is prone to breaking. This, fortunately, is a different scenario to chickens that break and eat perfectly normal in tact eggs to eat them (this is bad news and a habit I believe is hard to break). I suspect things will be just fine as they get the swing of things. You can always put some egg sized rocks in their nest boxes in the interim while you wait for your wood eggs in the mail.