Pre 2006 A&M settlement tax

I am dealing with a A&M settlement established in 1990 for 4 children of the settlor.
Having not dealt with trusts much pre 2006 i just want to check I am correct on the IHT treatment.

The deed includes a reference to “the specified age”, being 25 for A B and C and 21 for D. Beneficiaries born after the date of the 1990 deed the age is 18.
Upon reaching the specified age the deed states that the share/entitlement does not vest absolutely but retained on the following trusts.
The “following trusts” states the income of the share shall be paid to the child during his or her life. And there is trustee discretion to pay/transfer the capital to the child after the specified age.

A reached 25 in March 2005.
B in August 2006, C in March 2009 and D 21 in August 2010.

As A was 25 before the 22/3/2006 I believe that share of the trust is a QIIP and not relevant property. The rest of the trust will be a RPT and 75% of the trust is subject to principal and exit charges.
Is that correct?

Following a family breakdown the trustees consider that A, B and C have forfeited their rights to the trust and the trustees now wish to appoint out a property to D.
I am not a solicitor and the trustees need to take legal advice on this aspect.
Leaving that aside and assuming I am correct on the QIIP this means that on the appointment out I have:

CGT - 25% of the property gain cannot be held over as it is a QIIP for A. 75% can be held over.
IHT - 75% is subject to an exit charge. 25% is a PET by A.

Would be grateful for confirmation I have the tax aspects of this correct, or any other comments if not.
Thank you.