If I were you, I'd designate one day as your "anniversary celebration" day and mention it to the restaurant where you're having dinner. I'm actually going to be in WDW for my birthday, and want to have my birthday dinner at the California Grill. If the best day for our plans to eat there happens to be another day, I'm just going to call that day my "birthday" and do it that way. I'm not going to tell every restaurant it's my birthday and try to get free desserts everywhere, but I don't think fudging it by a few days to make it better fit your travel plans is a sin.