What a blessing that you are thinking that far ahead. Your children are surely fortunate to have parents that are ready to do the Lord's will in all things and anticipate the best way to approach the calling to the homeschooling lifestyle.
I can only answer this from a very personal level. I do not think that it is altogether necessary to have a program that provides grading and record keeping at the elementary level unless a particular family finds this to be a comfort for them. Some families like this and desire it in the homeschooling experience and others do not feel the need.
This is the beauty of homeschooling. It is both personal and unique to the family that chooses to educate their children in the homeschool. You will find that as you discern the calling to homeschool, you become more assertive about the type of education you desire for children. I feel that it is the calling from the Lord which empowers us to go forward into the task at hand. If the Lord calls us then He alone will continue to guide our efforts.
As far as high school there again it is up to the individual family. The homeschool movement is definitely gaining momentum and is widely accepted by many private as well as secular colleges. Big universities as well as smaller ones see the potential of recruiting homeschooled youngsters. It is a viable and doable method of teaching and no longer presents as a method that is on the fringe. I have homeschooled children who have gone on to college with no problems and adjusted well. The admissions offices of the schools they attended worked with us with regards to their homeschooling experience. It has not been a problem.
Keep praying for your vocation and ask the Holy Spirit to guide you and your husband to make the choices that are within the Lord's will for you.
Your family is truly blest with a mom who is praying to know the Lord's will.
Jesus, we ask that You send a fresh anointing of the Holy Spirit to this young mother. Give her confirmation to rest in the choices that she will make for her children. Lord, she desires to be within Your will for her and trusts in Your guidance. St. Angela Merici, pray for us.
Sending out a prayer,