I have been driving safely for over 15 years.
If you don't need to use the highway to get to where you are going then you can avoid it. Some people drive from their home to their bus stop, or local shop, or nearby job, and never anywhere else. You can certainly have a small, familiar route that you don't stray beyond, and do just fine.
You should probably keep in mind that there might be a requirement on your driving test that you go on the highway for a short while. You could find this out by perhaps asking someone who recently did it, or ask your department of motor vehicles (or whatever it is called in your area).
I do not think the highway is generally the most challenging place to drive. Even though the speeds are higher, there are fewer lights, choices, and possible distractions there also. I find the worst situations are in unfamiliar places with complications such as one ways or tangled up non-orderly roads that are easy to get lost in. They can be distressing and at the same time impossible to stop in and try to figure it out.
You could make a point of never going to such areas if you are concerned. There is no law that I am aware of that says that once you have a license, then you MUST drive everywhere.
Not all tests are the same. The examiner will ask you to drive only within a certain time period on local roads. You could choose the place you go to for your test, and make sure your driving instructor teaches you on those roads. If they are too hard, try another area. I failed three times before I passed my test - nerves and confusion made me make stupid mistakes. I still find I drive very well but if my husband is in the car the distraction can be a problem. I did not get my license until I was 29 - but part of that was lack interest, part was fear of the challenge.
If you drive somewhere and miss your turn, and find yourself going somewhere unknown and don't know how to turn around, you must know how to keep calm, find somewhere legal to pull over and work out how to get back on track. (thank good for GPS's and smart phones!)
I have to say though, that if your family are concerned about your ability to drive, then you should consider whether they have reason to be or not. I do not know you or them, and only hope for your safety. If you think they are underestimating you, then you could take some lessons and see how you go. Keep in mind that the roads are unpredictable, and if you fall apart at the wrong moment, it could have serious consequences.
You could avoid a lot of problems by being patient, practicing, leaving extra time for trips, studying your route before you leave the house, having a GPS and maps you know how to use and I'd say avoid travelling at night until you are very competent, same for very bad weather.