"Does anyone know if I can get an iMac at the actual APPL store with the bigger keyboard with number keypad? I see that as an option on the online store..."
My suggestion:
Try the factory (small, wireless) keyboard FIRST for a few days, THEN make your decision about a replacement.
You may find that you are uncomfortable with the feel of the Apple keyboard. I was. I've never gotten used to the "flat feel" of the aluminum keyboard in any of its iterations. But then, I'm an old guy who learned to type on manual (that's "non-electric"!) TYPEWRITERS. A keyboard with some "real feel" just works better for me.
There are many 3rd party USB keyboards out there that feel MUCH better. I'd suggest going to places that offer them (here there are Staples and OfficeMax and BestBuy), and doing some "test typing" on as many as you can find. Keep written notes on which you like best.
Then either buy locally or online.