Upcoming 4th and 6th Grader

I used to homeschool my children but about 3 years ago I went back to teaching and we put them back into public school.

Next year me and my husband have decided to travel and homeschool our youngest two children in the process. My youngest is my bonus daughter and has never been homeschooled. I have a feeling she is going to be behind in math. My son is going into 6th grade, and I plan to give them both the placement test for Elementary Arithmetic to see where they will fall in the books.

My main concern is my son, if he ends up placing at grade level that would be book 6, and so the program will only last us one year for him as I do not see any plans of creating a pre-algebra program with Simply Charlotte Mason (someone please tell me if I’m wrong).

So, is it worth it to try a new curriculum for him, even if it only lasts a year? Or should I find a program that does have a pre-algebra option so he can use it more than one year?

Lastly, what pre-algebra programs does everyone recommend. Something with shorter lessons like with Elementary Arithmetic would be preferred. We always used Math U See before, but I’m open to all options!