First of all, this is a job for a lawyer. It's not a DIY.
Especially if property ("the house"), and/or any other
reasonably valuable assets (such as a nice boat or a nice car),
and/or large amounts of cash, and/or a testamentary trust
are in play.
Now, if it's really true that everybody agrees that
the proportions should change, then an easier path
might (very, very "might") be something like this....
Get the estate settled first as per the will.
Pay the legacy bills, etc in the usual way.
Then, once, the various bequests are (so to speak) "free and clear"
in the hands of the respective intended beneficiaries*
there's nothing much stopping you (all) just giving each other
agreed amounts of (what by then will be your own) money,
so that everyone's happy.
If you can all agree, then it's probably a good idea
to get a lawyer to draft up some proper deeds about it.
This is for avoidance of doubt, and for reference in any later disputes.
Sounds pretty OK in theory, doesn't it?
Be cautious though.
Lawyers often find that people's... mutual good will and reasonableness...
goes away quickly once they have The Money in their hands.
Greed, grief, and emotional baggage can be powerful things.
------------------------------------------------------------------------
* Probably except for the stuff in the testamentary trust for the grandchild.
The pathway to shalom in the family might be to just leave that alone
(unless you can all agree to increase it).