Thank you for your question!
In the past, non-Catholics have used CHC for their children, and have been pleased with the materials. My suggestion is that you buy one of the Spellers and see how you like it. CHC's materials are very flexible, and you can always supplement your own religion program.
You might be interested in the following customer comment:
"I just placed my first order--a single copy of Language of God, B for my 8-year-old daughter. It is a lovely little book, and she happily set to work! I'm probably an unusual customer in that our family is not Catholic, but "high-church" Anglican, but we are grateful that you are making these resources available. We will order again! Also wanted to let you know that, both before and after this purchase, I have really benefited from the many resources on your website. So, again, thank you for the services and materials you provide to homeschooling families of faith!"
God bless you and your family!