Lately I've heard a lot about using a VPN/TOR portable router when on the road. Of course one could just set up a VPN on your single computer, but when you're traveling as a family it would make sense to use one of these devices. Just to be sure everyone know what I'm talking about, you can basically get an access point that you preconfigure your computers to access to and only your computers. Then when you get to a public wifi, you configure the access point to connect to the public wifi and then direct all your traffic through a VPN. These devices seem to sell as low as $20-30, or you can get them for free if you pay for a yearly VPN service (something like $99 / year).

I would think this would be up Mikrotik's alley, but I don't see anything like it. Does Mikrotik make something like this?

I would use simple VPN. Tor is slow and random outgoing addresses from all over the world aren't anything to be too excited about. If you just need to make sure that public wifi operator does not spy on you, VPN will help you with that and it's more predictable. Create VPN server on your home router, then get the cheapest RouterBoard (as the portable AP) and configure it to connect to VPN server and route all traffic there. And as a nice bonus, it gives you access to all devices in home network.