One way no minimise the CAT liability would be to give your grandchild 3,000 euro per annum, either in cash or stock. Your grandchild has an annual CAT small gift exemption of 3,000 per annum. You could open a bank account for him/her and put the money into it each year. If you live another ten years, that would mean the child will get 30,000.
Then, in your will you could leave the child the balence. If you give the child 30,000 in this way, and the remaining 70,000 in your will, the child will only pay CAT on the 70,000 minus the CAP group B threshold.
Do not put any monies into trust until you get legal advise. Trusts also subject to taxes.