First major bump in the road! Please help!

Hi! This is my first post so I'm sorry if I am not following forum etiquette very well!

My names Fi and I'm getting married in 8 weeks to my lovely Fiance Mark in Wiltshire, UK.

We have been together for 8 years nearly and I have always got on with his side of the family even though we are from quite different backgrounds.

All my planning has gone smoothly up until now and its been easy! However I have just got back from a week away to find a note on my kitchen table from my mother in law to be. I'll copy it on here to make it easier to understand:

Hi Fi

Alan and Robbie (Mark's Uncle and Cousin) would like to wear top hat and tails at the wedding. Please could you let Jackie (Mark's Aunt) have the details for the hire people? Thanks.

The only people I have already paid for suit hire for is Mark, his dad, his best man and my dad.

What do my fellow brides to be think of this? No one else is wearing top hat and tails except the men in the wedding party, my brother isn't wearing them and neither is Mark's brother. I feel as though I wasn't given much of a choice in the note, I certainly wasn't asked if it was OK!

I don't like the thought of them dressed in the same as Mark and his groomsmen because then it will just look unbalanced and I don't want to upset other male members of the family when they reaslise most of Mark's family have the same tails as Mark.

Hmm... maybe I am being bridezilla? Am I being unreasonable if I say that I would rather they didn't wear them? And how on earth do we broach the subject!! Mark's mum is lovely and I don't think she would mind but I know for a fact that Mark's aunt Jackie will probably be furious and I'm scared she will hate me. (Weddings do strange things to people)

His cousin Hannah is my bridesmaid, so it isn't as though none of them are part of the wedding party....

I don't know what to do ! Please can you give me your opinions and what you would do in this situation?

Thank you so much!