I think this situation presents us with an entirely new set of rules, because the old ones certainly don't apply. You're not illegitimate. And I am most certainly not going to have a group marriage. Haley seems very sweet, but while she knows me, I don't know her.
Could you please do me a favour and let me be the one to tell your mum what's happening. Then all three of us can talk about it afterward and you can ask as many questions as you'd like. Assuming she hasn't throttled me to death first.