:iagree: He wont give you more than you can handle. I suggest easing into things. Don't try to start school with a full schedule right off. Maybe Deschool for a bit and then add in a subject at a time until yuo are comfortable and then add in another and so on. If they are close in ages then definitely group them together as much as possible in school. This is a time and sanity saver!
As far as day to day life, I suggest getting a schedule together asap and getting the kids to help. The 8 and 6 yo's can load/empty the dishwasher, haul laundry to the laundry room, empty trash barrels, vaccum etc. Not only will it help you, it's good training they will need.
We don't do many outside activites now as it's just not feasible for us. They do 1-2 things and we have our home school co-op, which keeps us busy enough. You learn to pick and choose what is important to you. Maybe find something that everyone can enjoy together rather than seperate activities. Maybe take a year or two with NO activities. It wont hurt them. Spend time getting to know each other and forming your new family.
The most challenging thing I have found is making one on one time for each of them. When my older ones were small I used to rotate and take a different child with me each time I left the house.
The best? I don't know if I could choose one thing! I love having a large family. It's noisey, fun, busy, never dull, tons of love which just grows with each addition. I wouldn't change a thing if I could.
Blessings to you!