Hi Lisa,
I'm so excited to answer this question for you, since I am an unofficial "Star Wars Mom." Your 7 year old and I would be fast friends!
I see that you will be visiting at the beginning of June in 2015, which means you will be able to enjoy
Star Wars Weekends in Disney's Hollywood Studios. The Disney Parks Blog announced the dates of this special event earlier this month, and let me tell you, if your 7 year old is excited about meeting all kinds of Star Wars characters, and even a few Disney characters dressed in their best galactic gear, you'll have to attend this awesome event. It's out of this world!
Your 3 year old Disney fan will be able to
meet Sofia the First within Disney's Hollywood Studios, as well. At this time, she is available for a meet and greet in Animation Courtyard, outside the doors of stage 5 which houses the
Disney Junior - Live On Stage! show. Please note that characters available for meet and greets can change at any time, so be sure to check times on your My Disney Experience app and the Walt Disney World website once you are closer to the start of your vacation.
I hope this answer helps you, Lisa. If you have any other questions, please feel free to ask us at any time. We're always here to help.
Have a fantastical Disney day!