うちで皆でハロウィンパーティーするんだけど来ない？って英語でなんて言うの？

There are a multitude of ways to phrase this question. Above are a couple of examples. You could also use the persons name.... e.g.
ME: "Bill, would you like to come to my Halloween Party?"
BILL: "Love to. Where is it?"
ME: "My place! See you there at 10pm!"

When asking someone a question I always use the word 'would' as it is a little more assertive and positive.

You can also swap 'house' with 'home', 'place', 'joint'. e.g.
"we are having a party for halloween at my joint, fancy coming along?"

I am hosting a party and would like to invite you.

Would you like to attend my party?

Would you like to come to my party?

If you want to invite a friend to a Halloween party, in a casual way you can ask, "Why don't you come to a Halloween party at my home?"

1. I'm having a Halloween party, you're invited.
   私はハロウィンパーティーを持っています、あなたは招待されています。
   The word "invited" means to make a polite, formal, or friendly request to (someone) to go
   somewhere or to do something.
   "we were invited to a dinner at the Embassy".
   Therefore, this statement is a polite and friendly request to attend the Halloween party.

   2. I'm having a Halloween party, you're free to come.
      私はハロウィンパーティーを持っています、あなたは自由に来ます。
      The expression "you're free to come" is an informal way of extending an invitation to someone.

If you wish to invite someone or suggest something to someone, you can start the question using: "Do you fancy..?"
"Do you fancy meeting up early this afternoon and having a coffee in the shopping centre?"
"Do you fancy helping me choose a new pair of shoes in the department store later today?"
Wanna - this means 'want to'in spoken form.

Ask someone you would like to come to a party you are throwing for Halloween. There are several ways to invite somebody you would like to attend, for example;
1. ''Would you like to come to my Halloween party?''
2. ''I'm hosting a Halloween party, would you like to come?''

When you want to invite someone for a Halloween party and want to find out whether they would be interested in coming; you can say it in the following ways:
-I'm hosting a Halloween party at my place. Would you like to come?
-Do you want to come to my Halloween party this Thursday?
-I'm having a small gathering for Halloween at my place. Keen on coming?