Yes there is. With the Microserver as VM or standalone with Untangle installed in bridge mode. It's free and you can block and monitor your children's activity with it. With comprehensive reports.
Here is download link
http://www.untangle.com/get-untangle
Very easy to install and the interface is very easy to understand. It provides level 7 filtering, and is actually a UTM (Unified Threat Manager more than a firewall. Although its now called NG Firewall. It works very well in a VM on a Microserver or standalone.
Bridge mode is easy to setup and all your internet traffic will go through this on to your home hub. One thing you will require though is another network card. I recommend a CT intel 1000 which will install in the PCIe slot. Also if connecting many devices behind you will need a switch if you plan on protecting wireless devices as well you will need an access point plugged into the switch behind Untangle. All your wireless clients will then obtain internet via the access point. You will need to disable the BT wireless or password protect access from your Children.
If you can obtain another router and it can be set to access point easily you may not require the switch as the router may have enough ports for you to use.
Actually the best way in this situation is to use Untangle not in bridge mode but in router mode and set this as the front facing edge device instead of your homehub, and then set the homehub behind Untangle as the access point. This would save you having to buy or obtain the switch or another router. Untangle set up like this is the router a software one.
Another free way although too easy to circumvent is to use Opendns and setup filtering online. This will block certain sites, but it will not monitor individual machines. It will provide a report of all users using the connection and if the connection drops and your hub gets another IP well they will have full access again. So it's a very basic way of protection. If i were you try Untangle takes around 15 mins to install and works very well.
