1) I think you are lying. If not...
2) ask an attorney what you should do. Not lets run.
3) if $5 mil is less than 10%, then you have at least $51 million. Half of this money is your wife's. While this does not mean she can spend it as she likes as long as she is married. It does mean she can divorce you and get half which she can spend as she likes.
4) the estate tax is 5.5 mil per spouse. Meaning your wife can give 5 million away without estate tax considerations (though she can only give another 1/2 mil away if the current levels remain) without estate tax issues (see a CPA/enrolled agent).
5) if you gave away 5 million, you'd still have at least 46 million left. 46 million can give you almost 2 million a year for the rest of your life (using the 4% distribution rule of thumb). She/you can afford to do this.
6) 4% of a million is 40k a year for her cousins. They will likely think they can spend a lot more and will blow though the money in a few years. Then they will come back for more.
7) you will not be able to hide this forever. You will probably move into a better house. Quit work. Travel more. People will know something happened unless you flat out disappear.
The best approach is to give some relatives a yearly gift of 10-25k per year (depending on how many, and how much you can afford - this should come out of your 4%). Let them know this is all there is. Do not come back and ask for more. The only people you should give larger lump sums to are children or parents (and maybe siblings). But only if they are responsible with money.
It would also be wise to split the money into 3 (unequal) buckets. Household money, your money, and your wife's money. As example, if you had 50 mil after tax, then put 30-40 for the household, and 5-10 for each.
Fully educate your wife of money: gift tax, reasonable distributions rates, sensible investments, sensible portfolios allocations, etc, etc.