Because my youngest daughter took her sweet time getting here, I had to reopen with a 2 week old instead of an almost 4 week old... LoL
Like anything, you will just have to adapt as you go. I also agree that starting a little more gradually can only be a good thing. I ended up with only a p/t and a f/t, (plus my own baby, 4 year old daughter and 2 school age boys) and I am thankful for it. It was a bit of a hit on the pocket book, but better on my sanity.
The gals here gave me some great advice. It's okay to be a little less structured, and have a little more freeplay. So what if you don't do as many organized crafts and activities?? You will get back into the swing of things as you all adjust to the new person in your family.
I warned all the parents that there may be some days I look less than pulled-together, possibly meaning I open the door in my jammies, hahaha. I let them know that I would be nursing, but that I would be discreet, and I would be answering any questions that the kids had openly and honestly.
The kids didn't even bat an eye. They loved the new baby, and would pat her head and shush her if she was fussing.
It can be done, so don't stress too much. Before you know it, you'll be wondering where the time went. OH, and on rough days, where I maybe didn't get so much sleep or whatever; I was so grateful that I had a "job" that meant I could just sit on the couch and watch the kids play if I needed to!! Don't be afraid to rest if you need to.