Most people who inherit don't have any of their tax bill covered, so I wouldn't be overly concerned with you not meeting all of your children's tax bill. They are getting €150k of it covered by you already.
If you are in good health, it may be another 20 years before your adult children get any of this inheritance and they may closer to your age. They should have found their won way in life at that stage and have their own provision for retirement at that stage. Look after yourself first and ensure you have enough money to enjoy your own life before routine and comfort is more attractive than going out and doing lots of things.
Steven
http://www.bluewaterfp.ie (www.bluewaterfp.ie)