The crowds will be incredible! We usually go that week every year and this is the busiest week of the year.
Also, take some advice from me, add a day off from the parks in the middle of your plan. After fighting the crowds for two days, you will appreciate the time to re-group. It looks like it will be mild those days this year, so you may want to just relax by a heated pool or spend the day at Downtown Disney, or some other form of r-n-r. You won't be able to get much out of AK and MGM in the same day at this time of year. Best to add another two days to your plan, one for r-n-r and one for MGM. Four days straight and you will be regretting it.