by the sound of things, you are financially stable at the moment and have a pensionable job which should mean you will be financially stable in the future
Gordon Brown reckons you are wealthy so, imho, once you are financially secure in life, the next step is to have a healthy home life which it also sounds like you currently have.
obviously, im not putting money before family but rather putting their security first which includes financial security.......to me, this includes being able to look after them now and also have funds available to look after them in the future
changing career at this stage may increase the financial security but does it need to be increased?
im guessing that the only reason you may consider this is the challenge it presents.....is the challenge worth completely changing your lifestyly or not seeing your kids except when they're sleeping in bed at night or not seeing your wife except first thing in morning and last thing at night?(this may actually be a yes

)
i dunno what age your kids are but, again imho, having a parent, rather than a creche, care for them on a daily basis is very important......obviously, not everyone is in the position for this to be possible but when possible, it should happen like this
this turned into a slight rant but only because i know someone in a similar position as you who took on the new opportunity......his youngest kid hardly knows him and his wife has turned into the village bicycle.....as for him, hes working and drinking himself to death due to the pressure of it all
Edit: above two posts made in meantime and basically say what i said, with a lot less words
