I think you'll find that for even very small networks, Wireshark is going to be overwhelming to try to follow: it's collecting and showing the contents of every packet, even the smallest. You can take a capture file for a period of time, then save it and do successive filters for each host, and then again for each port/protocol of interest (e.g. TCP/80 for HTTP, TCP/22 for SSH, etc) but that's going to get cumbersome fast. You could write a shell script to analyze
tcpdump files, but really the issue is that packet dumps like Wireshark or tcpdump produce are just too granular: you don't need that much information.
There are some alternatives. The kinds of software that are used to determine bandwidth for 95th percentile billing could potentially be used here: something like MTRG. I suspect it would be a stretch, though. In general, the industry standard for this kind of bandwidth monitoring is NetFlow or sFlow. For a small shop there are a number of free and/or open source tools available. You'll need a flow exporter (your edge router may do this already; if not, there are a number of free flow exporters available, including this one) and a flow collector.