I don't think those rail road pictures takers with kids have much to worry about, in the UNLIKELY scenario where a citizen does make a report and the UNLIKELY scenario an officer actually responds to a "guy with kids taking pictures of a train".
I made a big charge on my credit card the other day. Card company called me to confirm the "unusual" activity. Frankly, I was glad to hear from them! Nothing wrong with tight security when you've got nothing to hide.