There is no question taxin, the toxin in yew is found in the wood and it is quite nasty, ever wondered why a yew post lasts so long in the ground? It is in the wood not just the sap so drying makes little difference, now when you drink from it how much taxin are you going to absorb? I can't tell you perhaps more if you use your quaich for whisky?
My take on it is I would be quite happy eating from a yew spoon myself but I do not make yew items for sale and the woodturners who made your quaich Toddy would be on pretty dodgy ground if you started showing symptoms of taxin poisoning.