It all hangs on whether the holding is on capital or revenue account. If they are part of Davids remuneration then the gain on sale is his income for tax purposes. So the ideal arrangement is to transfer them as close as possible to aquisition price to a family trust or some other entity. However this must be at market prices.
This minimises his gain for tax purposes. Then it comes down to the intent of thr trustees. In all likelyhood thay will have bought them for capital growth and I would expect the gains to be on capital account. However It must be clear that the trustees have not bought for the intention of resale or that they are traders ( unlikely). Even if they did buy for resale or acted as traders Trust income can be held as trustee income (taxable at 33%) or the income distrivuted to beneficiaries at their marginal tax rates. Certain restrictions apply to children