I am 70 yrs old and have 3 grown up children. Should I tell them about my Reverse Mortgage?

Yes, absolutely. The more people in your family that know about your Reverse Mortgage arrangement, the better for everyone involved. It is very important that you have a an honest & open discussion with your children (and any beneficiaries of your estate) so that they realise there will be a debt/loan to clear with the lender when you die. An honest conversation now with them may avoid some complex or unpleasant discussions in the future.