Being that it is the beginning of a new school year, I have seen a lot of questions come up on the various homeschool groups I belong to about how to home school your older children while you have a baby and/or toddler (or more) running around.
Based on my past experiences (I homeschooled like this for 12 of my 15 years!) and what I've been reading, there really are only a few tried and true answers. You probably know them by heart if you've been homeschooling for any length of time:
1. Keep a special basket of toys for the baby/toddler to play with during school time only.
2. When you really need to focus, assign an older child to watch the baby/toddler for that time period.
3. If the baby/toddler will cooperate, have a gated off area that he/she can play in while school is going on. This will allow you to focus on your students and know that the baby/toddler is safe.
4. Keep them in the school room with you and give them their own "work", even if it is just scribbling on a paper, to do.
5. Take full advantage of nap times (if there are any) and make sure the older kids have independent work they can do when necessary.
And that, folks, is about as good as it gets. This time has to be one of the most challenging times in homeschooling. There will be good days (meaning the baby/toddler are happy and content and the older children want to learn during that same time) and there will be bad days (the baby/toddler is crying and fussy all day and the older children just don't want to learn).
I really don't mean to sound like a pessimist (because I prefer to think of it as being a realist :), but the best you can do during these years is to take advantage of the good days and know that on the bad days you did the best you could and that your children are still learning things by helping out around the house and doing their independent work.
You can have a plan...you can have structure...but you still might not be able to make everyone cooperate at the same time! It is still good to have that plan and that structure, but realize that part of homeschooling means being flexible. Try very hard to love these challenging years, knowing that they really will be gone before you know it, instead of letting them push you over the edge. If you have an over-the-edge day, just do like Noah Webster's mother used to do and throw your apron up over your head so no one can see your face and pray for strength (I always loved that story :).
May God bless you as you struggle to find what works during this very busy, but wonderful time in your homeschooling career!