6yr old boy/girl twins here.....
+ 4 older boys.
I have 1 book for all the kids. Seperated by year. Specific LO's with just them, the bigger kids and their activities etc....
Copying the LO's to take with them is a cheap and easy option.
Id drive myself nuts trying to scrap each one seperately and the big kids. I scrap our lives, all of it together. They can figure out what they want copies of when Im dead.
I have a friend with 4yr old twins and an older child. She does seperate books for all, its time consuming, slow and repetitive....according to her.