I'll try to keep this as simple as I can.
If I have a laptop that is 2-4+ years old chances are that it probably doesn't have wireless N if it was an entry line to moderate system so if I try to connect to your AP I wouldnt even see it since I cant "speak" that frequency. however for $20 I could buy a wireless N USB dongle if I knew that you were using wireless N only and then attack it.
You might want to consider loading DD-WRT (alternative firmware) if your specific hardware revision is supported. Check out http://www.dd-wrt.com/wiki/index.php/Linksys_E4200 but since it's a work in progress you might want to just craigslist the old router and replace it with something that will meet/exceed your specifications. Buffalo makes some models with DD-wrt from the factory. I've setup several of these for small cafe's and offices and they have more than most need as far as a feature set goes.
This should give you most every option you could ask for.
Next I would take a look at where you have your router and how far you want to go from it, then change the power settings to increase or decrease the transmission power to assist in securing it based on distance. The only flaw with this is someone could build a 25dBi antenna and amp the signal in order to reach you.
If you are paranoid about people getting in, stick with hardwiring everything and just disable wifi, because time will always defeat encryption. A long password today might take 1000+ years with $500 of video cards but in 2-3 years from now that same $500 might take a week to break the same passkey.