Who was going to look after your son when the tickets was originally ordered?
You need to stop with the making excuses. It comes across as passive aggressive. It comes across as you reacting and doing a tit-for-tat.
You could have easily said.
"X. I know we ordered those tickets before. I have forgotten about them. Next week I am very busy at work and have made commitments that I cannot back out of. I will not be able to look after our son the whole time of the concert. So let me see what I can do with work. You will have to find arrangements as well. I will ask at work tomorrow and let you know the answer. Please keep me in the loop as well. Talk to you later."
End conversation.
Think about who was going to look after son in the first place.
Go to work. Ask. Get answer. Send answer in text or email.
Carry on.
Work towards this.
As this is what detachment is about.
Flowers always make people better, happier, and more helpful; they are sunshine, food and medicine for the soul. unconditional love is awesome!