2.- INFORMAL INVITATIONS:
It's also common to use suggestion forms in more informal situations to invite other people to join you in doing something.
USEFUL SENTENCES:
Let's + Verb
How about + verb ending in -ing?
What about + verb ending in -ing?
Shall we + verb?
Why don't we + verb?
EXAMPLES:
How about eating out today?
Let's go for a walk.
Why don't we go to the theatre?