|but to start I suggest putting your office in it's on workgroup.|
It takes nothing to change a computer from one workgroup to another.
While I applaud your enthusiasm, your posts weren't worth adding here as my solution is the securest way to segregate the "guest" network from the private network. Your "solution" wouldn't provide any real segregation or security I'm sorry to say.
As for two separate WLAN's, if that's what you want and both SOHO Router's are wireless capable, again, my solution is the simplest and the most secure. You would simply create two separate WLAN's. The "guest" would be unsecured and unecrypted (at least, that's how we setup our 'guest' WLAN here at work). The private one would be encrypted (WPA2) with a strong password. You could even make that SSID hidden.
All in all, the point I'm trying to make is simply this, to keep the two networks segregated, the best way, bar none, is to have them on different (separate) subnets and arrange it so the guest network cannot access the private network. It doesn't matter (in this particular case) if the private can access the guest network.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.