Welcome to planDisney, Margaret!
Since I also have a family where the children outnumber the parents, I understand your concern. I think you'll be pleasantly surprised to find that many attractions at Walt Disney World Resort have bench or theater-style seating that can accommodate your family configuration. Even on attractions that commonly seat two Guests per ride vehicle, such as
Peter Pan's Flight,
Haunted Mansion, or
Buzz Lightyear's Space Ranger Spin, it is possible to fit one adult with two small children. Attractions with a limit of two Guests per row are generally coaster-style attractions. In this case, depending on the ages of your children it might be possible to seat your two older children together with a parent in the row behind.
For attractions that you have reserved
Lightning Lane access with
Disney Genie+, everyone in your party does not need to enter the Lightning Lane together at the same time, although each Guest may only use the Lightning Lane once per attraction within the Lightning Lane time window.
I think your family may benefit from
Rider Switch service. One adult can wait with any Guests unable to ride, while the rest of the party enjoys the attraction. Then when the first party returns, the waiting adult can board with an additional Guest. Rider Switch may be used with either the Lightning Lane or standby queues.
For any attractions where the seating configuration may be a concern, talk to a Cast Member at the entrance to the attraction about how your family might be best accommodated. They can let you know the best arrangement for your family, and issue a Rider Switch entitlement if necessary.
Please stop by planDisney again with any additional questions you may have. We are always happy to help. Enjoy your magical vacation!
Anne Marie