Windows Domain Topology doubt ?

Dear Friends,

i have to design a network topology for an existing company which is already runing without a domain infrastructure.so can anyone help in this here i want to configure this domain with windows domain AD structure they have many shopes all over the country and outside the country.
my doubt is
1.can i join all remote shopes computers(every shopes wid 1 or 2 pcs) in the domain ?
if i do
2. it will effect the network i mean it will make network link slow ?
cause links are not that much faster.

can i deploy SUS server in a topology like this ?
also antivirus server ?

my company 1 location wid more than 12 computers what to do wid this office ?

pls help me u can send ur detail advice in this mail also san7up@gmail.com

thank you...