Your 6509 config looks correct, except did you notice that you have the interfaces shutdown?  When you bring up the trunk, I would enter the configuration as follows:

Do a show int on each interface you are bundling to ensure that the configurations are identical. Then enter the following:

interface range Gi1/1/1 , Gi1/2/1

  channel-group 3 mode active

This will place both interfaces into the port channel and bring it online. The relevant configuration from the underlying interfaces should be copied into the port channel interface automatically for the most part, but you can check it afterward by doing a 'show run int Po3' and adding any configuration lines that are missing. (In the past I have seen that some things like portfast do not get copied automatically.) Your 4948 configuration should be similar. As far as I know, the channel-group command is universal in IOS, but I am unfamiliar with the 4948 specifically.

You will have a spanning tree event when you first bring the port channel online but by using LACP and if you are using RPVST+ the impact should be minimal. All the same, I would do it during off hours or low usage, if possible, and plan for some minimal disruption.