Alison, I'm so excited for your Princesses to visit Bibbidi Bobbidi Boutique! My little Princesses loves it!
Traveling from park to park can take some time, so be sure to allow yourself plenty of wait of time in case the lines are long.
From Magic Kingdom, I would be sure to be line to board the bus to Disney's All-Star Movies resort no later than 2:15pm-2:30pm. This ensures that you have plenty of time to get to your appointment. Also, keep in mind that the Disney Festival of Fantasy Parade begins at 3pm daily, so crowds may be difficult to move through as guests are searching for the best spot to watch the parade. On a good note, lines for the resort buses may be short. Your ride back to the Resort, will take approximately 10 minutes. Once you arrive at the resort, waiting for a bus to Disney Springs may take up to 20 minutes or longer depending on city traffic. Once you board the bus to Disney Springs, the ride is about 15 minutes and the walk to Bibbidi Bobbidi Boutique from the bus drop-off is about 5-10 minutes.
If you arrive at Bibbidi Bobbidi Boutique a little early, no worries, you can take some time to see the newly renovated Disney Springs.
I hope that your Princesses love their magical makeovers! If you have more questions, please come back to visit the Disney Parks Moms Panel!