If Wireshark is installed in /Applications/Wireshark.app, and you have a small shell script called, for example, "wsopen":
#! /bin/sh

in your \$PATH, you could open multiple files from the command line with wsopen {file path}. (If there were a Launch Services command-line tool to find the path of an app, that could be made to use the installed path even if it isn't /Applications/Wireshark.app.)