Well, I can think of a few things you can do but first of all, what is it about flying that makes you nervous? Is it a lack of control or just a claustrophobic feeling? If you try to pinpoint your issue maybe you can confront it a little bit, be honest with your kids so they are aware that you are nervous because your specific feeling instead of making them think it's something wrong with the flights your family is on.
As a flight attendant, I can tell you that a lot of people are nervous but manage to just take their minds off of the worrying by using videos, music, really good books, some use alcohol and some use drugs. I've a had a few INCREDIBLY nervous moms who sit seperately from their kids and their father and watch the crew the whole flight for signs of trouble. In 14 years flying I've only had about 2 women at this extreme and their kids seemed fine sitting with their fathers. Also, can you try to book direct flights to your destination and maybe go somewhere short like Bermuda (assuming your flying out of Boston) or one of the Carolina beach destinations, minimizing your worries?
I'm sure you already know this but flying is very safe and although there are incidents in the airline industry all the time, a vast majority of them happen on the ground during taxi in or out, ironically this is when most people relax and take off their seatbelts. Yes, take off and landing are critical phases of flight where bad things can happen at a rapid pace but be alert to changes (this is where I think it's not such a good idea to be on drugs or not completely sober) and noises that are strange and the crews's reactions to them.
Personally I am much more worried about who is controlling the cars around me while I'm shuttling my kids about town than I ever am about flying. I mean people drive while on prescription drugs, drunk, texting, talking, eating etc. It's crazy! Pilots on the other hand are highly trained, there are always two of them with procedures in place in case one suspects the other of being unable to fly and not to mention that aviation is one of the most highly regulated industry in the USA. There is a rule for everything, just in case!
All the best,
H.