Dumb terminals Thin clients vrs regular

Help, I’m part time network admin for small not for profit. Expanding LAN to a WAN to put a branch office on network.
New CEO insists on dumb terminals, thinks it will reduce admin time. Other people tell me differently. Can dumb terminals be mixed with regular desktop PCs on network?
How much more bandwidth would dumb terminals need over desktop PC?
Art Bottomley
artbottomley@cs.com