Son Light is not Catholic.
When you say you want to incorporate a “religious subject,” do you mean you want to teach religion? If so, I would recommend using the Ignatius Press series, “Faith and Life.” You can buy the book(s), or you could have your children take the course online - I think it’s called, “my Catholic faith delivered.” We use the actual books, and depending on whether you just want to read a little with them each week, or want to do full scale lesson plannings, you could just buy the student book, or also get the teacher’s manual.
ignatius.com/Products/CategoryCenter/3159/FaithandLifeThirdEdition.aspx
mycatholicfaithdelivered.com/home.aspx?pagename=FaithAndLife
For the Kindergarten level, Ignatius Press has a catechism series called “Image of God” that has a Kindergarten book - “Who Am I?”.
ignatius.com/IProducts/175610/who-am-i-kindergarten-teacher-workbook.aspx
I would recommend highly Catholic Heritage Curricula (CHC) also. Their second grade lesson plans, you will get a lovely Sacramental Preparation course. I’ve used this with my older 2 children, and plan to use it with my younger ones also when they get to 2nd grade.
If you’re looking for other subjects, but with a religious perspective, you could use other materials from Seton or CHC as well. Both have spelling and grammar programs, which have the Catholic life built into the exercises. Seton has Catholic history books, and CHC has Catholic science books and some really nice Catholic story books.
Otherwise, I would recommend getting a collection of religious books - the St. Joseph Picture books are great
sacredheartbooksandgifts.com/index.php?m=4&s=0&mc=0&sc=0&pd=9780899423005, as are the Catholic Children’s Treasure Box series
chcweb.com/catalog/product_info.php?cPath=1_162&products_id=300 . Either way, browse through the websites of both CHC and Seton, and you will probably find plenty to choose from.