Is it normal to shed a few vellus hairs if you have a full head of hair?

Of course it is normal to shed hair. If we did not shed hair, it would never stop growing. Hair lives 2-6 years and the longer it lives, the longer it grows. There are documented reports of individuals with hair over six feet long. Considering that hair grows about 1/2 " per month or 6" per year, a six foot length of hair must live 12 years. 
The hairs that fall out are in the catagen phase. It takes a few weeks for hairs to die and fall out. The hair detaches slowly from the bulb, the hair shaft falls, and the follicle enters a dormant period. 

Yes shedding small hairs is normal. As the proportion increases one becomes more concerned. However, shedding a few is normal.

hair shedding is present in normal people as we lose and replace every hair on our head over a 2-3 year period of time