Translation:I hope that you can come with us tonight.
Ich hoffe, dass sie heute Abend mit uns kommen kann.
I'm not a native German, but I believe that the infinitive needs to agree with the pronoun here, so:
Sie (sing. formal You) können
sie (plural They) können
sie (sing. She) kann
If you had the umlaut in place in your sentence, I believe it would translate to:
I hope that they can come with us tonight.
I hope that helps.