In Need of Record Keeping Ideas

I was just showing my husband our son's new math curriculum we have.  Then I showed him the phonics/reading curriculum & the math manipulatives set (online as we've not ordered them yet) that we're going to be using as well.  I was explaining to him a bit of what I read in the math teacher's guide introduction about not giving a letter grade to each and every lesson.  It made me realize that while I have most things figured out (minus the organization - working on that & it will likely involve more purchases), I haven't learned about record keeping yet. 

I absolutely will be record keeping starting with kindergarten.  I'd like to do two "mid-term" reports during the year and then a final report card at the end.  So - exactly how do I do this?  There is a plan I have so far & I would appreciate some feedback from anyone who has been homeschooling a couple of years already & has done record keeping.  I'm also interested in hearing from anyone who is also starting out who has a solid plan for how they will be record keeping grades.  My plan is to buy one of those cardboard sliders that I've seen in teacher's stores for calculating grades.  Then I'm sure I can find some report cards online to order to keep track of it all.  I'm thinking that should be good for each assignment I choose to grade, right?  So then how to I average those altogether for the mid-term & the final report cards?  Thank you in advance for your suggestions & ideas.  Any pictures and links to materials would be great as well.