I am making a program for an upcoming graduation ceremony, and I'm not sure which is correct:
"Friends and family of the graduates are welcome/welcomed to stand during the ceremony"

Thanks!

you should use WELCOME because WELCOMED is only used as PAST tense NOT as PRESENT tense

example :

*all of you are WELCOME to my house.

*My mom WELCOMED my friends in our house YESTERDAY

In your example, you want welcome.

It is possible to say "You are welcomed" though. For example,

When you arrive, you are welcomed by a butler.

In this case, welcomed is a past participle, which, like all adjectives, can be used with the present tense.