There's a new trend to use they instead of he/she/it or the possessive their instead of his/her/its. In our department, we tend to rewrite instructions to use the plural they/them/their.

Be careful. Don't just do an automatic substitution to the plural. You need to make sure that all the words match.

Incorrect:
Everyone is bringing their favorite dish.

Correct but Awkward:
Everyone is bringing his/her favorite dish.

Correct:
All of the students are bringing their favorite dishes. (You may need to do a little revision.)