A.M.
Hi C.!
My son was 23 months when my daughter was born. I had her naturally but the week before i knew i was going to have her (i had her 2 weeks early) my son became really clingy wouldn't sleep by himself only wanted mommy etc. everything you are expressing. I also became worried. One of my clients recommened that my husband and i get small gifts for my son, wrap them and pack them in the hospital bag. When he came to visit us at the hospital we gave him a gift but said it was from his baby sister. He quickly became attached to her and was kissing her is thanks. We also had a "bigger" present at home when we arrived back home. I really think it helped him be OK with everything. When baby was born he went to my friends house and he did great! visiting us often. When we got home he also did great. He just wanted to help mommy and hold his sister. I had him help me out and feel included by having him bring me her diaper when she needed to be changed, i also would have him bring me the wipes, birp cloths, balnkets etc. I even let him "help" me change her diaper a few times. He would also help my husband bring me water, snacks etc. When he were out i would ask him to watch him sister while in the stroller and make sure she stays happy. He would tell me when she would cry etc. I really think that it kept him feeling in the loop and made the adjustment easier. My daughter is 7.5 months now and he has not been jealous of her at all. I spend "Gavin and mommy" time together everyday! Usually when she takes her morning nap. Or if i need to go grocery shopping i will leave baby with my husband and i will take my son.
For right now have your daughter help you with getting ready for baby. Folding clothes for baby, getting your bag packed if not already, etc. Just keep talking to her about it that is the best way to prepare her. I let me son watch "A baby story" on TLC with me one day to show him that's how baby is going to come out of mommy. it did not traumatize him but i think made him more aware.
Let me know if you have any questions. I could keep going on about how we prepared him...lol
Good Luck and CONGRATS!
A.