Welcome to the Disney Parks Moms Panel Maria!
Two days at the Magic Kingdom sounds wonderful! No worries - I've often visited the parks alone with my boys and we are able to ride most of the rides and have a great time.
Here are some suggestions that you may want to wait until you have 2 adults present:
* Buzz Lightyear's Space Ranger Spin - You can absolutely do this ride with the 3 of you but there are only two lasers. When the 3 of you are riding, you can control the spinning action of the attraction vehicle and let your daughters each have a laser. Go back when you have 2 adults so that you can battle the Evil Emperor Zurg too.
* Tomorrowland Speedway - You can all 3 probably squeeze into one car but both of your girls will probably want to drive so you may do this one with 2 adults.
* Space Mountain - This has a height requirement of 44". If your 6 1/2 year old wants to ride, the day to go will be when both are adults are there. If both adults want to ride you can do the
Rider Switch.
* Splash Mountain - This has a height requirement of 40" and more comfortable to do 2 to a seat (its tight with 3).
* Big Thunder Mountain Railroad - This has a height requirement of 40" and you can all 3 fit in a seat but both my boys like me to hang onto them and I slide around like crazy.
* The Barnstormer - This has a height requirement of 35" and you'll need to ride 2 to a seat.
Other than those, I think you'll find that the 3 of you will be able to easily enjoy the other attractions together.
Please feel to visit with all of your planning questions. Its a pleasure to assist you!
Wishing you minnie magical memories :-) Allison V.