Help!

I have a 12 yo DD and a 6 yo DS.  I have found homeschooling with 2 kids in opposite ends of the age spectrum somewhat challenging sometimes.  They have widely different needs at very different times.  It’s almost as though I have 2 “only children”  My daughter is currently doing 7th grade work using SCM materials.  We are in our 4th year of educating the CM way and also with using SCM.  She is currently doing most of her school work independently which is wonderful because it has allowed me to be more free to work with my son.  He just began “formal schooling” in January when he turned 6.  He has not been ready to work on much of anything related to school aside from counting, reading, putting together puzzles, etc. until this last summer and into fall at which time we began working on learning the alphabet and the sounds, number recognition, writing the numerals and his name.  Up to this point his learning has come through play.  He is pretty phenomenal in what he can build with Legos, blocks, and Lincoln Logs.  He seems to be very mechanically inclined and soaks in and learns from his surroundings.  In January something clicked and he was ready for actual school time.  We began MUS Primer, in which we skimmed over several lessons because he quickly grasped the concepts.  We began SCMs Delightful handwriting and just last week we transitioned him into working with SCMs Delightful Reading Kit.  He is doing very well with all of those things and we will continue these things throughout the summer.   I give all of this back story so that it will hopefully give you some insight to hopefully give me some advice on a couple of questions I have regarding school for next year. 1.  How do I “place” my son for next year’s work?  Do I plan the year with the idea that he is in 1st grade beginning in the fall?  or do I continue doing Kindergarten work throughout the fall semester and transition into 1st grade in January?  I am unsure about how to go about teaching in this manner for early elementary since we didn’t begin CM until my daughter was in 4th grade.  Any help, insight, suggestions, advice would be very much appreciated in this area! 2.  My son has always listened in on our Bible/History/Geography lessons, but has not been an active participant.  Is it age appropriate for him to begin those lessons if he were to start 1st grade in the fall?  If so, would I have him join in where my daughter’s history cycle is (Middle Ages) or should I begin him on his own history cycle? Thank you in advance for any and all help!  I am overwhelmed at this point and need to hear how other people have done things in these regards. Charity