Try to remember that one of the greatest advantages of homeschooling is the gift of freedom. You do not have to (nor should you want to!) duplicate the school environment at home. When I was feeding the baby, we all cuddled up on the couch and I would read to my older girl. When I cooked dinner or baked cookies, we practiced reading (the cookbook) and using measurements. When I took the baby for a walk, we'd talk about the trees or stones or insects we discovered. Our walks would be followed by a trip to the library to further explore items of interest or to answer questions that came up. I'd pop in an educational video in the afternoon for my daughter, and I'd rest with the baby. In essence, we continued living and learning, just like before. Only now our activities were more varied and interesting.
At five-years-old, your son is not going to require a lot of academic work. He does not need a curriculum or lesson plan. Most boys his age are not ready for pencil and paper learning anyway. Please take the time to read at least one book about homeschooling before the baby is born. Homeschooling: The Early Years - Your Complete Guide to Successfully Homeschooling the 3- to 8- Year-Old Child or The Homeschooling Book of Answers, both by Linda Dobson, are good choices. Also, visit our How to Homeschool information center for more ideas and advice.