With the verbs "come" and "go" you'll never use "going to"-*We are going to go.../ *They are going to come..., but-We are going.../They are coming...(present continuous).
Also, use present continuous for an agreed meeting and "going to" for an intention or decision or a future plan. Present continuous for things you would put into your diary as a reminder, usually with verbs of movement or activity. And present continuous for a future arrangements between people, usually for near future.
I hope this will help you some.
- For Teachers