gweny70, you only weigh 293 or so, you aren't that big. I started riding again when I weighed well over 300 pounds!
As to the Wally World bikes, yes they will get you from point a to point b, however I would really recommend going to the local bike shops and see what they suggest. I know Giant has a couple of really nice, simple bikes that are under 300 dollars on my local shops floor! In fact one is called the simple. The other I'd suggest looking into is the Suede. Both of these bikes are available as coaster brake models that are very dependable and few complicated parts.
Schwinn also has a few nice bikes, but don't buy the ones in the big box stores. They are not the same bikes as the ones your local shop will have. And there are many more brands out there worth the time to consider them.
I rode a Kmart Huffy for 3 years, I spent well over 150 dollars keeping my 90 dollar bike performing. I still had to make compromises. The shifters never really worked right, and I had to skip a gear as the bike never wanted to stay in that gear.
There are also other areas where the quality of the components is just not there. You don't need to spend 1,000 dollars on a bike to get a good one, but I think you should spend more than 90 dollars to get a functional one.
You are also not going to want some skinny tires nor do you want the big knobby mountain bike type tires, look for a cruiser or comfort type bike. You will then be riding in a more upright, comfortable position.
The biggest thing is to buy a good bike and the right bike to fit you and your riding needs. Unless you know how to fit a bike to a person, please take my advice and go to a local shop. If you don't get a comfortable bike that suits you and your riding needs well, you won't enjoy riding and will eventually quit. Or hurt yourself, and that is also no fun.
There is a resouce on the web that I visit frequently, it is
http://forums.mtbr.com/ There is a forum there for riders classified as Clydesdale's.
http://forums.mtbr.com/forumdisplay.php?f=95
Don't be offended by the name of that forum and you can overlook that this is primarily a mountain biking site. There is a lot of great info for larger riders there, check it out. There is also a commuting forum on that site that is also a great source of info. A lot of the people on that site are like me in that I have a coupe of bikes and not only a mountain bike.
Good luck!