I just bought the Nikon D7100. I am wondering if I made the right decision on this camera. For my PI business, I will be taking close-ups, long distances, night time photos and videos.

I also will need the pictures and videos to be time and date stamped. I have heard that this can be difficult to do when transferring the photos or video from the camera to the computer, I have a Mac. I understand it is on the camera but once transferred the date and time are lost. Any help with this?

canon and nikon are equally excellent - just depends on your individual preference.

Is there a "special" lens for videotaping and a different lens to use for photos? What about lenses for day versus night use?

I am also looking to buy a SLR camera for my son. He is planning to take a photography course in college so I would like to get him a nice camera as well.

I understand that you can NOT interchange lenses from Nikon to Canon, if this is so, then should we both have Nikons?

I welcome any and all advice.

Thank you in advance!

Would not have been my choice for night photos, but for everything else, you bought the best in class. The close-ups, long distance, etc. is your lens choice.
Check cinema lenses for video, but others will do also.
Transfer will contain all the data and numbers. Should not matter whether a Mac or PC. Not difficult at all.
Assuming you would stay with Nikon, suggest the D3300 is an awesome entry-level camera.
There are adapters made to use lenses on different brands, but I am not well versed in what fits what. Thinking Nikons can be used on Canons, but not the other way around? Perhaps someone else can explain in better detail.