I work with all different age groups and recently have notice several people with veins on their faces close to the surface - some spider- some bigger - what are the causes and what can help to reduce the veins

It may be from skin ageing, especially if it was exposed to sun a lot. Prevention is in using sunscreens with both UVB and UVA filters - UVA is the main cause of skin ageing.

There are several other causes of spider nevuses: liver diseases, alcohol, hormonal changes - esp. in women... so hard to tell "what helps".