Below are IRS regulations concerning EIN of Trusts.

No time limits for the required obtaining of a new EIN are set.
The simplest is to do nothing for one month, for three months 
or for nine months, then effectively terminate the Trust by
closing all accounts with the old EIN, by transferring all assets
to accounts with your social security number.

There are other ways to proceed each of which has its pros and cons.
We can discuss them when and if you wish. My advice is that you proceed
in the manner most congenial to you.

I have reviewed the terms of the Trust which provides that any sums disclaimed
by you are divided equally among your four children. 
In this regard also I have no opinion and no advice.

https://www.irs.gov/businesses/small-businesses-self-employed/do-you-need-a-new-ein

Trusts

You will be required to obtain a new EIN if any of the following statements are true.

    One person is the grantor/maker of many trusts.
    A trust changes to an estate.
    A living or intervivos trust changes to a testamentary trust.
    A living trust terminates by distributing its property to a residual trust.

You will not be required to obtain a new EIN if any of the following statements are true.

    The trustee changes.
    The grantor or beneficiary changes his/her name or address.