New and worried, Rainboe has a well deserved reputation to keep up. But, I think he is probably right.
Despite your apparent desire to become airborne you really don't sound ready or mentally prepared. Human factors can play a big part in any accident and worry and stress are often contributory factors. Hiding behind your moniker "New and worried" only serves to underline your fear that something awful will happen. If that is how you feel then I would suggest that you postpone you flight tomorrow until you can get to grips with this. Otherwise it will affect you training and, potentially, your safety.
Why do you feel you are being selfish? Are you committing money to do something you always wanted to do but feel you are denying your kids something? Are you really afraid of dying? Are there underlying worries that are only surfacing now?
Bottling up problems only serves to harm other people and bringing this to a forum suggest that you haven't articulated your fears to your nearest and dearest.Until you can put your two boys to bed at night without having premonitions of disaster perhaps you should leave aviation alone.
Take you family along tomorrow, explain to the boys that this is something Dad has always wanted to do, that it is safer than crossing the road, and get them enthused! They will soon be looking forward to a jaunt in the aeroplane and you will feel better about yourself. It's only a lesson. Do you think your instructor has this fear everytime he leaves his family in the morning - I Blinking well hope not! Yet he is sitting next to an absolute novice to whom he will voluntarily hand control of the aircraft!
I don't think you feelings are necessarily at all normal and yes, I do have kids and yes I have taken them flying and yes they love aeroplanes too. No I have never felt as you describe and I have been flying since 1979 and and fly regularly as a passenger as well as PIC on a range of big and small aircraft. I have made numerous PAN calls over the years as a result of various technical problems and one mayday as a result of a mid flight fire. This was extinguished and we made a safe emergency landing. In the same time I have had one minor road accident but, I would regard aviation as much safer than driving.