Depending on the location of the inline check valve that is fine. The purpose is to keep the line full when the pump is off. The backflow preventer is for protecting the city/county water system from contamination. You are not on the city/county system so don't need it which you already know. The check valve should be as close to your pump system as possible to keep the line filled are far as possible. Save pumping time to fill the line each time. Also quieter because less air to squeeze out of your system. Also protects your pump from spinning backwards from draining mainline water. JMHO Aloha

There are 2 types of backflow preventers: reduced pressure principal and double check.

Reduced pressure must be used with a public water supply, and double check should be the minimum to protect an aquifer (using a well).

A single check valve may be allowed in your area but does not provide 100% safety. Even 2 check valves in series is better than a single one.