Hello, Cyn!
Advanced Dining Reservations are usually available to Walt Disney World Resort Guests at about 180 days prior to check-in. As such, you should be able to book a reservation for Tusker House (great choice!) at Disney's Animal Kingdom just a few more days from now.
Regarding a reservation at Chef Mickey's, if there isn't one available when you first try to book your meal, call Disney Dining at (407) WDW-DINE (or go online) from time to time to see if one becomes available. Lots of folks make dining reservations, then either change the dates of their trip or change their daily plans as the date of departure gets closer, so it's possible that you can snag someone's cancellation at that time. During more crowded times of the year, it can be difficult to get a reservation at this popular restaurant as the dates get closer; however, it can't hurt to try!
Hang in there! I'm sure if you call on the very first day that you are able to reserve your week's reservations (once it's 180 days from your check-in, you'll be able to make all of your reservations for the entire week), you'll be successful! Good luck!
Feel free to send more questions as you think of them; we love to help!