Beneficiaries access to Trust accounts

Firstly, apologies for the very limited information, as this was just presented to me today as a general enquiry.
My client recently lost their father-in-law and believes that he had arranged a lifetime Discretionary Trust, before he died, for his grandchildren. My client’s father-in-law and his wife were two of the trustees. He is not sure if there are any others.
He is worried that his step-mother-in-law (who is still alive) is keeping the Trust a secret and has been using proceeds from the grandchildren’s trust to pay for her own benefit eg her holiday house etc.

The grandchildren are still minors, nearing age of majority. Can they, or the deceased’s son, demand that the trustee(s) provides them with a copy of the trust and give a breakdown of what has been spent and distributed?

The other problem being that they don’t know who all the trustees are and wondered if there is a way to obtain all the information, without approaching the step-grandmother at this stage.

Many thanks for any guidance you can give.

btw I have advised him that we would need sight of a copy of the trust deed, to see how the beneficiaries have been identified etc. If it clearly just states “grandchildren” then they may have a claim. However if the step-grandmother is an additional beneficiary it will be more difficult.

I feel 90% certain that a named remainderman can request from a trustee the following,

The terms of trust (will and or trust deed)
Confirmation of who all trustees are
Trust accounts which clarifies what the trust owns

As a remainderman they have a right to check the stewardship of the trust if I am correct in saying. If a trustee refused to show the above what is the next steps through?