Welcome to the forum!
Any form of racing (or sport) is going to involve some amount of risk of injury. I think I would agree with you as to the Bando cars being somewhat safer due to the roll cage and 5-point safety harness. As with karting, there are different divisions for the Bando kids; (1) BANDITS: (Drivers between the ages of 8 -11) as of January 1, 2018. (2) OUTLAWS: (Drivers age 12 and older) as of January 1, 2018. Some tracks require restrictor plates (either Blue or Red) to keep speeds down. Other tracks may have a gear rule. This is a spec class racing vehicle; There are only certain things you can do to them; And only certain parts that you are required to use.
Another thing to consider is the cost. I have no clue as to costs for karts. I do know that the tire bills can really mount up to some serious cash. With that said; Bando cars aren't exactly cheap to get started in either. Plan on spending between $6,000 - $10,000. Remember, besides the cost of the car, you will need proper racing attire (or gear), membership fees and likely want a few spare parts, tires, etc...
Here is a link to the rule book. You may want to read through it and see what is required.
http://www.uslegendcars.com/documents/2018-rulebook-word---final.pdfIf you have further questions, I will do my best to try to answer those for you.
Best of luck!
Steve