Based on the info in your post, it looks like you have the correct settings for your network.
You can confirm in another way as follows:
Open AirPort Utility and click on the AirPort Extreme on the left. Look for the AirPort ID of this device on the right and jot that info down. Do the same for the AirPort Express.
Then, move your laptop very close to the AirPort Express, hold down the option key on your Mac while you click on the fan shaped AirPort icon at the top of the screen, and note the BSSID. That number should match the AirPort Express, indicating that your Mac is connecting to the Express and it is extending properly.
If you see the BSSID of the AirPort Extreme, that would indicate that the Mac is connecting back to the "main" router and the Express is not extending the wireless signal.
but how could one verify that they are connected to express, not the extreme, if they are using a PC?
I donl't have a PC here to check, but maybe a Windows guy will see this and tell us.
Also, Is there a way of changing the airport settings through the iPad?
AirPort Utility will run only on a Mac or PC
I tried (ipconfig/all) but couldn't see the difference between Base and extreme. Everything in my house is Apple, except for my laptop. I love my Extreme and got an Express to extrend it to the outside. Without getting off subject, I would love to verify that my express is extending my network. Like you said, I hope a Windows guy will see this and tell us. Thank you for your help and response.
Sorry I'm also a Mac guy but if you read through my first post it might help you to find this out via Airport Utility as it should work on windows too. At first I made the mistake of Joining a network with my Express instead of Extending a network and the clients list will appear different then how I described it above. Seems like the most important things are to make sure your Extreme is set to Create a network and you must check the box that says Allow this network to be extended. In your Express select Extend a network and actually the router did the rest on my end...
Also, it might help if you try the equivalent of iStumber on Windows to see your networks. Although I only have one network name in iStumber it shows me that I have 3 networks so 2 are from my Extreme and 1 from my Express.
And finally and this might do it, you can go back to the Client list in Airport Utility to see which station you are connected to. That's what I was doing before Bob's easier solution which unfortunately doesn't seem to help you at the moment...
Hope this helps a bit as I just went though this. I'm just entry-level here Bob is the true expert and is always helpful! :-)