Alone, alone??? That will be hard. Together? I might let them loose in the same "land" as soon as they ask (not the same park, I'm talking fantasy land or tomorrow land etc). My girls are 11 and 8, and the 11yo is the more timid. So I don't see it coming up for another couple of years.
The boy, I will keep handcuffed to my side until he is 18 and I am no longer legally resposible for his actions. lol.
The boy, I will keep handcuffed to my side until he is 18 and I am no longer legally resposible for his actions. lol.
) Now...a year ago when we were there, DH and I wanted to ride TofT and they did not. So we bought them a snack, sat them on the bench outside the exit of TofT, and gave them strict instructions to sit there, eat the snack, and not move. There was no wait for the ride, so we rode, came out and they were still there !!

My ride w/ her on the Indy Speedway last summer took years off my life.
How can you not steer a car that has a rail guiding it where to go? 
and I have a feeling that they will want to be on their own a little more.
They love being with us. It is my dh and I who beg to go off alone for a few minutes LOL