Although Ashkenazic practice is to conceal the night of mikveh immersion, it is ok for a few people (preferably women) to find out about it if that is the only way you can get to the mikveh that night.
Alternatively, it is permissible to come up with an excuse (even one that is not truthful) about where you will be going. You can say you are going to shul, or that you are going to visit a neighbor, etc.
There is a strong preference for immersing on time. However, if none of these options work for you, and your husband agrees to delay immersion for one night, it is permissible to delay mikveh until Motzai Shabbat.