Thank you for your question. I am not familiar with [the Catholic, classical program] materials. However, if you are switching to CHC in the fall, you will want to consider that you will be switching from 'one school to another'. So, there may be some differences in the materials. Fortunately though, you will be homeschooling, so if you find that there are gaps in your children's learning, you can go at a slower pace. Also, you might find that they are ahead in other areas, in which case you can accelerate the pace. With CHC's materials there is no set schedule or requirements, so you have the freedom to choose the materials and the pace.
God bless you and your family!