1. Firstly your wife cannot relinquish the rights of your minor child by any such undertaking, she has no rights to do so, the child would claim the amount after becoming major by age ignoring the fact that the mother has already availed the same, because he can very well deny to have received the same and moreover she cannot deprive the child's rights during the minority of the child.
Therefore the clause that the one time settlement is made for the child alone may may not be very effective especially when the child claims once again after becoming major by age.
Now by removing the wife's name from this condition, she will become eligible for a claim for maintenance under section 125 cr.p.c. at a future stage even after divorce, hence it would be advisable;e that the present clause what you have inserted in the agreement shall remain in the same manner without any alteration to the whims of her advocate.,
2. The above answer suits this question too. You may better not agree to remove the clause at the instance of her advocate.
3. The challenge to her future claim can be decided at that time if at she returns to court with a claim in the future in this regard, based on the circumstances prevailing at that moment.
4. As a matter of fact she nor your child cannot claim any share out of your immovable or movable assets either now or at any stage in future, at least not during your lifetime.
In fact she cannot claim any share in your property after getting divorce from you even after your lifetime.