To expect siblings to get on grrrrrr

[BreakfastMuffin]

So I made a plan to go out this afternoon to an outdoor centre where we have a membership (so it's free) for some fresh air and excersise. On way back I wanted to take my 2 Dcs to a climbing centre we've not been to before. All were looking forward to it. I then thought I'd ask a friend and her 2 kids to come along. They couldn't come today but could do tomorrow. I told to 2 Dcs ( 9 & 11yo) whether they wanted to go today on their own or tomorrow with their friends, and that's where it went all wrong. One wanted to go today, the other one tomorrow.. They were arguing and couldn't agree. I got cross and said we're not going anywhere now. I'm cross at myself for even telling them the options but I was trying to consider their opinions... Should I have listened to one child and gone against the other? No idea how to deal with this better.

Why should they have the same opinion? Haven't you heard of sibling rivalry? Giving 2 children a choice when you can only do 1 thing is never going to end well.
Make a plan and stick to it.

Me and my sister were like that.

Now I am 37 and she is 35 and we haven't spoken properly for about 5 years and that is just the way we both like it.

Yep don't give them the choice, they aren't mature enough to see all the consequences of the decision, including what could happen if they disagree.

You make a decision and explain it to them, then if they really disagree discuss it.

Errr this isn't not getting on

This is just having different opinions

Agree that Giving 2 children a choice when you can only do 1 thing is never going to end well.

Well, I could potentially do both, take one today one tomorrow but it wasn't my plan...

I used to be like this with my Dsis.
We hated each other.
We are in our 40's now and have been best mates since I was about 17!!!