Take the information I present below with a grain of salt - opinions are like...well you know.
Before evaluating anything in this arena, you'd have to decide what level of management/intervention is required on your part and how much 'trust' you're going to place in managed services and crowd sourced/off-the-shelf configurations.
If you're not technically savvy, then something like a hardware solution (firewall/proxy e.g. Sonicwall, Watchguard, Cisco ASA, Fortinet, Barracuda, etc.) or roll-your-own (e.g. pfSense, etc.) probably isn't an option.
If you're not desiring something you have to manage rules, configuration, etc. either, then OpenDNS might be off your list on top of the aforementioned hardware. Another point of interest is that you can also choose to use other people's/companies white/black lists and profiles if you want to reduce your management of services (including Covenant Eyes, or X3watch). Drawbacks here are just that you don't know that you might disagree with what constitutes 'safe' content/sites vs. someone else's criteria based on your family's age profile(s) and personal morals. As someone mentioned earlier, if your kid is tech savvy, a lot of these integrated services can be bypassed relatively easily, even if you know how to lock down access to the configuration permissions on the device.
Devices/services like HomeHalo and Circle try to take a lot of the day-to-day hassle out of managing content filtering and internet access. However, they come with a trade-off in that you lose some ability to configure what that content looks like (site specific or customized white/black lists). Furthermore, because they are account based, your usage statistics are tracked and managed by a 3rd party. It wouldn't surprise me to find out that companies like Circle use data collected from its customers internally as well as leverage its install base to sell 3rd party access/content delivery as part of its revenue model (although this is complete conjecture). However, there is no doubt that your usage information is accessible to them. It just depends on how comfortable you are with that (note: your ISP also likely collects this kind of information to a certain degree so it may be a non issue to you).
Regardless, these solutions (currently) only work for in-home devices and not with roaming/cellular devices, although Circle appears to have something in the works (because it's service based).
I know this doesn't provide a 'go here, buy this' answer, but to me the arena of 'content filtering/management' is a broad topic without a one-size-fits-all solution. If you narrow down your areas of comfort, willingness to manage, and usage desires it might be easier to help assess a proper solution.
I know I don't have first hand experience with things like Circle or HomeHalo, but if that is your preference someone here might - or be able to direct you to more reviews/opinions on them outside of just Amazon, etc.
YMMV.
