Where do you live?
The best thing for you to do would be to go to a homeschool convention and wander the curriculum fair - go around to booths and look at what people are offering for curriculumn. There are a lot of secular/non religious options out there. My family was very Christian but Mom used a lot of secular materials for us - especially for things like math and grammar where the “Christian” stuff was just injected in on top and seemed stupid. Check your area for secular/non-religious homeschool associations (there are often these around though they can be sort of liberal).
Of course, if you've already DONE your homework before you go to the Fair, you might be able to take advantage of some special pricing on the curricula that you already know will work for your family.