Funny things shares. Lots to consider. clients can fall into the trap of letting the 'tax tail wag the tax dog'. Some of the decision making will depend on how urgently the money is needed clearly.
But perhaps to go into the decision making pot:
not all of the holding needs to be sold in one go. sell some to protect past gains.
are the shares about to go ex dividend - will a dividend be missed if they are sold at the wrong time
are they going up/down in value (consult Mr Gekko as we all know greed is good!)
can any be kept so the holder can take advantage of any share holder perks
and of course there is good old risk to consider. Is your life over and will you be getting lunch from the bin on the street corner if their value falls to zero overnight (mind you even that comes with a tax break!)
Watch any advice given though as its regulated