Welcome to the Apple Community.
I'm assuming this is a simultaneous dual band router. I don't actually have such a router but was considering the new Extreme which also has this feature.
The first thing I'm wondering is whether you will have the choice which frequency to join on the Apple TV, since iPhones, iPads etc will automatically join the best network, but if you do then I don't see any reason you shouldn't be able to join either.
The second point worth mentioning is that you may not necessarily wish to join the 'n' network. 'n' is faster (although 'g' is faster than the Apple TV can write received data anyway - I think the 'video networking' mode you mention is just advertising bunkem) and it is also likely to suffer from less interference, but it is also shorter range than 'g' and is blocked more easily by walls and other solid objects.
That's exactly the situation I'm into right now.
I just bought a dual band Linksys EA4500 and assigned 2 different names for the 2.4 and 5ghz networks. I connected the Apple TV to the 5ghz (since it's N-only) and my Macbook automatically decided to connect to the 2.4ghz one. I manually dissconnected and reconnected it to the 5ghz one but now the Airplay icon isn't showing up, only when I'm on the 2.4ghz does it show up.
Any thoughts/help on this?