I don't portend to know anything but if this were mine I would offer these suggestions. My changes are bolded:

Our Halloween bash is an annual affair,
You and a friend are invited, if you dare.
A word of caution, you should take and be aware,
Those attending should be ready for a frightful scare.

The evening brings a dire situation to light,
And those with weak constitutions take flight.
Many(deleted involved) will be in too deep before they learn of their plight
And will receive their deserved reward; a heart-stopping fright.

The time is drawing near when the jack-o-lanterns glow,
And the ghouls and goblins take to the streets, all ready to go.
So come enjoy the antics of those brave enough to show,
and watch them come unglued as the libations start to flow.

I like what you wrote, it's quite good.