I found this simple instruction. It's targeted to blocking porn sites but it works for any website. Blocking videos is a single click.
How to Block Porn on a Computer Without Software | eHow
www.opendns.com
Opendns has been around a long time. One of the good things is that the 'administrator' does not have to be on-site after the local router is set up to use opendns as it's DNS server. The blocked message is configurable so indeed it could say something like 'Streaming videos in MY RV Park is not being a good neighbor.'
There are daily reports generated that show all network traffic and bandwidth consumed for each domain/site name hit. If you missed one it will show up in the reports and you can add it to the block list.
So that's step 1.
Step 2 is to find the QOS (Quality of Service) setting on the router(s) and disable it. QOS gives media packets top priority. Disable it and they default to the same priority as all other network traffic. On a marginal bandwidth connection this makes videos very difficult to watch. It does the same with VOIP (Skype, magic jack, Ooma etc.)
The hardest part of setting his up is getting administrator access to the router(s) to set the DNS address manually to what opendns uses.
There are many other ways to accomplish blocking. This is only one of them.