I know this isn't a new thread, but I figured I could throw out some ideas too.
We moved to 5 acres and ended up getting pregnant the month we moved in. (Surprise!) NOT expected. So, After 9 months I had a newborn, 2.75 yr old, 5 year old, and 9 year old. The month after I had the baby we got our first horses (we board some for income), the next month my DD got two dairy goats (We had one that died the month after I had the baby) along with the chickens, dogs, and such. Honestly, it was easier for me than trying to do it pregnant since I *could* leave the baby for a few tasks, and stuff like that. We now have 4 dairy goats, board 3 horses, and have lots of chickens and ducks
For the baby -find a back carrier that you love. It is priceless. My 4th grew up on my back. I think he was on my back before 4 weeks in a wrap. It's SO much safer with farm work than a stroller, and much faster and less complicated. At almost 18 months he's about 50/50 now- on my back sometimes, or walking around, etc. I have some "Safe places" I can stash him for a short amount of time, but my back is the best. The hardest is if it's pouring sheets of rain, but we work it out. He rode on my back to pull a water wagon with me from 3 weeks on and is now highly addicted to the 4 wheeler,
2-4 year olds LOVE to help. They can learn rules. If we are doing something dangerous like cutting down trees they have a specific place they have to be- on the porch, in the truck, etc. He helps unload the truck full of mulch, catch ducks, and can lead the goats. Now that he's 4 sometimes he actually helps. If he gets tired of helping he will find some dirt and play with his trucks.
My 9 year old is great. She does help a lot. Sometimes I give her the choice. If it's raining and I can't do the chores with the baby on my back I'll ask if she'd rather do chores (she gets paid for the horses, and the goats and ducks are her animals) or stay inside with the baby. She can do all the chores herself, but she's a natural animal lover and most of the animals are hers, so that's a little different than if they were all "ours" and she wasn't into them.
I can be done. My hubby can do stuff in a pinch if DD and I are both really sick, but he just doesn't know the animals as well as we do and doesn't always know the changes that happen as we add new animals, they grow up, etc.