Hi there. Congratulations. I'm six months pregnant and just back from a week at Disney World with my DH and my two girls (2.5 and 3.5). We had a great time but it was tiring for sure. We took breaks in the middle of the day for the girls but I was definitely benefiting from them as well. Being early in your pregnancy, I can assume you're going to feel tired too so rest when you can.
I rode with my girls on everything in fantasyland plus some others.. (peter pan, small world, dumbo, pooh, aladdin's carpets, snow white, etc.). I saw a pregnant lady - maybe 4-5 months along- getting off of Pirates of the Carib. but I personally didn't do it. I also rode Soarin and Nemo. I'm not really into "big" rides even when I'm not pregnant so I wasn't missing out on anything.
We took advantage of the rider swap a few times. We used it so that my husband could ride a ride with one daughter and then go back and ride it with the other in cases when I couldn't ride but they could (Barnstormer, Indy Speedway, Safari @AK etc.)
You're going to have a great trip. Plenty of foods to choose from when you are having those "I could eat.... But definitely not that..." moments.
Good luck!
Lesley