Btw I take it you've tried EMDR OP? I only ask because it's become accepted only relatively recently, that's all. Supposed to be effective for trauma related issues.
Anyway - I imagine the kids are just suffering from that well known teenage lack of empathy - they literally cannot imagine what it's like to have your body and mind going crazy going NOPE NOPE NOPE when you're in certain situations. They are still engaging in magical thinking, that just because they WANT your reaction to be different means it instantly will - but in reality, how many people have instantly got over a severe flying phobia? I wouldn't want to bet my summer hols on that being true!
Can confirm you can get to a lot of places without flying. Malta. Morocco. Turkey. If you stop off here and there to break the journey up, it can be fun. Shorter distances you can just travel straight through (e.g. Switzerland, Germany, Austria, south of France, bits of Spain, you can do in a day).
Lastly how much of the "oh but Mum must come too!" from DH & DC is just because people are scared of change? You could take off for a mini break with a friend and see if they've gotten fonder of the idea by the time you get back.
Are they just wanting you to come so they don't have to organise/dogsbody themselves? In which case, shame on them, and clearly they need the opportunity in order to grow as people! 
However, if it's just that they love you THAT MUCH, then, surely, they can bear your absence for the sake of your happiness, eh?