To add a couple simple ideas to what you already have done or the suggestions of pp here, some things that worked for us include:
--At nighttime, we have special time. At least a few times a week, my kids and I (including the 2 year old) lay down on the bed, I put a few drops of aromatherapy oil on our bellies, and we take turns rubbing their bellies, and they rub my belly and feel the baby. It's funny to hear what the oldest two say, "Oh, I can feel the baby's hair, Mom!"

No, they can't really, but it's great bonding.
It also naturally invited conversation about when the baby will "come out" and what it might be like, and the kids ask questions they have. For a two year old, this is special time with Mommy, and can continue into a new routine once baby is born and they still need to feel special with Mommy. (Everyone gets a special tummy or back rub with Mom, baby and toddler, too)
--Be naked in front of any child who might come in to the birth, that way when they see Mommy naked in labor or at the moment of birth, that is one thing at least that is normal to them. A lot of people dress or shower with children present so it may be common for you, or it may not. This is one of those YMMV suggestions, and can be done to whatever comfort level you or your child needs.
My oldest was not present for our second's birth, but our second was present for his little brother's birth. Labor was blase for him, he was more interested in hopping in the birth pool (which I was not okay with being in transition at the time); my sister helped him to come in right as his brother was born, and he and his older brother patted baby's head, and hung out for the weight check and first nursing, then hopped off to go play again. It was no big deal, but I sure was glad to have someone there to help with the kids.
Even though I prepared them as best I could, birth is such a fluid experience, you never know what it will be like, and so I am pretty open to whatever happens, if the kids need time away from me, fine, if they want to be near and can have good "birth manners", fine! (I like having my kids around)--my no. 1 rule is no jumping and yelling in the room while Mom is laboring! But I have all boys

) It can be very special and feels more normal for me to have my own little family around me, but if it gets too chaotic, I have a helper to step in with the kids as needed.
Good luck with everything! Can't wait to hear your birth story
