In my experience, the more you open things up for opinion and choice, the harder you are making your life.
Start the group chat with key decisions already made by the key people. That way, people are just deciding if they can/want to participate.
Initial email:
Hi All,
Welcome to "Staceys" Hen Do Group Chat!
On 1st June 2026, we plan to rent an 8-bedroom house for the weekend in [location].
The price per person will depend on how many are able to come. An estimate is [£ per person] if 12 of us attend. There will also be additional costs of [£p.p.p] for food and drink. We'd love you all to join "Stacey" for this special weekend. Please let us know if you would like to join - insert poll on whatsapp chat -
~ you might want to add details about bedroom allocation, because that would 100% be a factor in whether I decided to go or not. I'd be pissed if I paid my deposit and then found out I'm on a blow-up bed in the kitchen! ~
Follow up-email:
Hi guys, We've had 10 people confirm they'd like to join us! That would make the cost £x per person, and £x additional per person for food & drink. If that's agreeable to you and you'd like us to proceed with making the booking, please send a non-refundable deposit to me via bank transfer by [date]. Final balance will be due by [date]. Would people prefer to make small monthly payments toward this, or a larger one-off payment nearer the time?
If your availability has changed and you can no longer come along, please let me know.
I wouldn't book anything or be on the hook for the finances until I had deposits in my account, with a deadline for final payment made clear.
If there are travel costs associated with getting there, it might also be worth making that clear upfront too. Basically, be transparent with people.