Hi, Gwynn! Congratulations on your exciting baby news - babies are the absolute best!
There is a policy at
Walt Disney World that prohibits children under the age of 7 from riding unaccompanied by another person who is at least 14 years of age. So, although your 8 year old will be able to ride, your 6 year old will need to have someone who is 14 years or older ride with them.
Having said that, there are a lot of attractions you can do together. You won't at all hinder their experience. Attractions such as
Pirates of the Caribbean,
Jungle Cruise, and the
Walt Disney World Railroad have ride vehicles that will accommodate multiple people. Other attractions have ride vehicles where you can sit three across, or two in front and two in back.
Many of the attractions you can't ride because of your pregnancy, they may not be able to ride due to
height requirements. And there are so many other things that you'll all get to enjoy together.
If you will have another grown up with you, you can also utilize the
Rider Switch Service. That will let you wait with one child while someone else takes the other one on the ride, then you can switch when they're done.
Have a wonderful vacation with your children, and I wish you many happy, healthy baby wishes!
Anna