Doesn't matter at all. Never re-mortgage a house. Off-springs still living with their parents into a later stage in their lives just happens. If you and your wife are happy about this and also your children accept your rules, then enjoy your family while you can.
Explain the inheritance 'financial buffer' to them if you can.
There will be a time that they will have to fend for themselves. That will be the time that you will no longer be around.