How can I increase the lock screen delay?
Try using Delayed Lock - works with ICS but you need to be rooted ONLY if you want Pattern Lock. PIN and password lock do not require a device to be rooted to use this app.

There's a trial version which I highly recommend you try and use before making a decision. There are also available free plugins to automatically keep the device unlocked while connected to a specific WiFi network / Bluetooth device or at certain locations.