Can't decide between friends...

As you have already accepted the first invitation and the individual budgets have been organised accordingly, it would be really shitty to drop out because you have a better offer.

If you didn't want the first invitation you should have declined.

Me too!!
Op the cat is out of the bag now so you can just say as your friend isn't welcome on the birthday trip that you will be spending the weekend with her - but l would still say in all honestly l was having doubts after l heard there would be kids coming too. If she decides not to speak to you again, well that's her choice. If it was me, l'd possibly be pissed off for a bit but wouldn't lose a friendship over.

Why are you so bloody awkward

That's not the truth either is it?

Ths truth is that you were never going and were going to make up an illness at the last minute.

I would just be totally honest and say you rarely see your best friend so "with regret" you won't be coming as you can't pass up this chance to spend time with her. It was the (not best) friend who said she couldn't come on the birthday trip after all.

This!

All you needed to say was that it wasn't your thing with kids and you'd pass this time.

Now it's become complicated because the weekend away friend will think you're dumping her for something better.

When in fact you weren't ever going to go!

Why can't people just be honest instead of tying themselves in knots.

Because if everyone secretly decided they weren’t going to go but just lied and said they were sick at the last minute no one would turn up! She’d have an utterly shit birthday. But if you tell her in good time “sorry but the change of plan (kids coming) means that this just won’t work for me” she could have a rethink. Honestly you just sound like a flaky nightmare to me, I couldn’t cope with friends like you.

You’ve made a right mess of this.

You could have declined the invite ages ago. You could have declined when you discovered you had to host, but instead you asked if you could bring your friend to this lady’s bday weekend away - why? You didn’t want to go in the first place but wanted to bring a stranger into the group for someone’s birthday?

Now you’re just going to have to cancel and bday friend is obviously going to feel like you’re choosing the other friend over her.

If you pull a sickie the day of, your bday friend is going to know you’re lying and that you just want to stay home with your visiting friend.

You planned to involve DH too!

Suggest working on your assertiveness.

In which case you should have had the guts to cancel when that became apparent. People who plan to lie their way out of situations like this are dishonest and weak. Just be grateful the arrival of your friend from overseas has provided you with a ready made excuse.

I really hate when people feign sickness to get out of something. Everyone knows you’re lying and it’s not a nice thing to do. Why can’t you just be honest?

Don’t lie about being ill, just say now you can’t make it and send a nice bottle of something and a card via someone else who is going to the weekend.

short / no notice is a downer for the organiser, even more so if they suspect dishonesty.

Because it's the mature thing to do.

Just tell her you'll do something with her afterwards but that you're spending that weekend with your friend as you never get the chance to see her. Tbh when she mentioned you wouldn't know anyone there except her, I'd have backed off. When she mentioned the children would be there, I'd have run for the hills.

I get not wanting to go on this weekend OP but you should be upfront about it and cancel in good time.

This is a perfectly valid reason. Just say you understand, but unfortunately it means you won’t be able to come. Wish her a lovely birthday weekend and hope to see her soon.

@Ethicaldebacle - you say you don’t like confrontation but you would have been letting birthday trip friend down much more by dishonestly claiming to be ill on the day than telling her upfront. Most people don’t like confrontation. Part of being an adult is learning to have tricky conversations in a way that is respectful to all parties.

And now your US-based friend is over, you’re actually just throwing over the arrangement with birthday trip friend in favour of a later offer.

Can you see that your fear of confrontation is actually causing you to behave dishonestly and unfairly to your birthday trip friend?

I’ve been in similar shoes to you, OP, and realised that I was letting those around me down really badly with my behaviour.

In your shoes, if you value your friendship with birthday trip girl, I think I would be having a frank and honest conversation with her and apologise for letting her down and explaining your thinking.

I think BFF is the perfect and genuine excuse. You can't leave her alone. You offered birthday friend a compromise (bringing BFF). She said no, fair enough, but the result of that choice is that you can no longer go.

You don't need to make up something about illness which isn't true. Personally I would have politely dropped out earlier and said I wasn't keen on the kids being added to the dynamic and would look forward to treating her to a grown up celebration lunch some other time soon instead. The friends bringing kids may have no real choice because no childcare but you aren't obliged to go to something that wasn't what you signed up for.

You should have declined the birthday weekend before-hand if you didn't want to go. Obviously now it's going to look to the birthday weekend friend that you've dropped her for someone else.
Careful wording but but be honest - along the lines of your friend from overseas has just been in touch and it's your only chance to see her. Sorry, etc. and offer to do something else with birthday friend very soon on a 1-2-1?