Using a B1/B2 visa with a valid L2

I was just approved for a single entry L2 visa and I have a valid B1/B2. I want to go to the US for a few days with my B1/B2 on a preliminary trip to get some things organized before I enter officially with my L2 a couple of weeks later and then be stuck in the US for the duration of my L2. Is this possible or even a good idea? I’m afraid they’ll force me to use my L2 in immigration and then not be able to go back.