In the top left of the WhatsApp "Chats" screen there is a little-used
feature called "Broadcast Lists".
This lets you send the same message to
multiple contacts at once without them knowing, a bit like the
"Bcc"
button on emails.
Go to Chats -> Broadcast Lists -> New List -> add contacts and
write out your message -> hit send.
The message and their reply will
appear in your private chat with each person, but with a little
megaphone icon next to it. Your contacts won't have any idea that the
message was sent to anyone but
them.
