transferring video to DVD is not really the way to go as once you have them on DVD it is very difficult to get them off the DVD, onto the Mac, and edit them.
What you need to be looking for is a method of converting the Analog tapes to a digital format. This is usually done with a Digital Bridge. Converting Analog to DV is the first step in getting the video into your iMac (iMovie) in an editable format.
Google will be your friend when looking for one of these. Dazzle made one, not sure if they are still around but if they are then eBay or Amazon are the best sources.
You do not mention what vintage your iMac is but Firewire is the best method of transfer. If you have a Mac with no Firewire then USB is the next transfer method.
This article may help you: http://www.macworld.com/article/1002418/converters.html
Details on your iMac will also help
What is the best and fastest way to transfer Hi8 tapes from my Sony CCD-TRV98 Handycam to my iMac (v10.8.5) so I can edit and burn them on DVD?
Exact steps please. Also include exact cable descriptions so I can refer to them easily.
From what I see, my camera has a "S" video out connections, a A/V out connection, and a RFU DC out connection.