A: You should have more than enough storage space and memory for running the publishing program, assuming it is a MacOS compatible program. 1TB is storage. Computer storage is a lot like a physical filing cabinet, it tells you how big the files you keep can be. If you run out of room, you can't store any more files without cleaning out old ones. 8GB is memory. Computer memory is somewhat like short-term memory in humans. It is the capacity that the computer has for holding the information it is actively using for programs. 4GB is most likely referring to the storage size needed to download the program. 1TB is about 1000GB, so you will have enough space for your program, based on the information you provided.
Q: I know this can connect to WiFi but would I need to get anything else for it to connect??
A: If you have peripheral devices like printers or scanners or cameras or external hard drives then you would need USB cables for those, except if they are expressly wireless diverse, in which case you WiFi network would suffice for everything. If you are just surfing the web and doing eMail then you don't need anything else (other than the power cord that connects you to household power).
Q: can you upgrade the memory?
A: Yes, you can upgrade to 16GB.
Q: Is this computer good for kids "gaming"?
A: You must love your grandchildren a great deal. My son has Autism and we are able to run all of his therapy games with some fun apps and iTunes without difficulty. However, if your grandchildren are serious gamers, i.e. competition gaming this system will not work. You will need to find out what type of games they play. Nancy Drew mystery, Braid, Where is Waldo, I Spy series, The Witness and anything Sesame Street will all work well. XCOM2: War of the choosen will need a better graphics card, and faster processor. In all a more powerful system is needed for these types of games. Half the fun is getting them to talk about what they like doing. Go online with them and find the types of games they like to play. Then you’ll know what system you need.
Q: Does this model come with the Retina display?
A: Yes this Apple has a Retina display. Great display screen.
Q: Does this computer have a thunderbolt option?
A: Yes, every iMac since 2011 has built-in Thunderbolt. The 2017 models sport a newer variety of Thunderbolt called Thunderbolt 3 (or sometimes called USB-C). The earlier models would have Thunderbolt 1 or 2. You need a different cable for the Thunderbolt 3 (USB-C) than for the earlier Thunderbolt 1 or 2, which use the same cables.
Q: Is there an option to install MS window OS instead of MAC OS?
A: Yes, you can install Windows in 2 ways. One is by Boot Camp, where the Mac can run Windows on a separate partition and behave pretty much like a full-fledged PC. The other is by installing special software (such as VMWare or Parallels) that installs Windows on the Mac as a separate program so you would be running Windows INSIDE the Mac operating system. The details of how to setup these are too much for this Q&A box but you can look them up by Google'ing How To Setup Boot Camp Mac or How To Setup Parallels Mac.
Q: Can i get 512 G SSD instead of the 1TB drive?
A: Not factory. You can install an SSD but unless you've taken apart an iMac before I strongly suggest against it. It is easy to crack the screen replacing it. Since an iMac is stationary, your best bet would be to buy the SSD and an enclosure since booting from a USB ok an iMac still moves extremely fast. You could format the internal drive after you have installed OS X on the SSD and have a large amount of storage.