Hi Stacey,
As a mama who has taken multiple Mouseketeers by the parks by herself before, I just wanted to encourage you that you can do this! I'd encourage you to take the trip and make memories with your kiddos!
The great news is that most
attractions without a height restriction utilize bench-style seating that should accommodate all three of you comfortably. For rides with height requirements or attractions where you'd like to spread out a bit more (like on
Toy Story Mania! where you'll all want to be able to play along), you'll see signs that state that children under age seven must be accompanied by a person who is 14 years old or older. In my experience, most Cast Members will allow you to sit just in front of or just behind your kiddos. There have been some occasions, however, where they interpreted that to mean that anyone under seven needed someone 14 years or older directly next to them. That's always been our experience at
The Barnstormer, for example. Since your older kiddo is already seven years old, they would be able to ride alone (if they're comfortable with that!), and you could sit with your little one directly in front of or behind them. I'd simply encourage you to ask Cast Members at attraction entrances where you're not sure how seating arrangements will work to make sure they'll be able to accommodate you in a way where all three of you are comfortable!
I'm so glad you stopped by planDisney with your great question, Stacey, and please let us know if we can help with anything else as you're thinking through the details of your visit. I hope you and your Mouseketeers have a truly magical vacation together!
Missy