Ds is at a newish school - he was so happy to have been invited to a karting birthday party - turns out the whole class were invited - details were - the date- the activity-transport provided (it’s a 80 mile round trip) and a request of Amazon vouchers for present. In the last few weeks since they broke up I’ve been updated with further texts from the mother of birthday boy asking for deposits for the karting (£20) and the remainder on the day (£30) THEN that was followed up by a request for £20 for the transport 
This morning she (in my opinion) has the gall to request we pack a generous picnic with ice packs and pack extra so the birthday boy doesn’t have to bring anything
I was going to decline following the minibus request but ds was so happy to be invited - I think this is the final straw and I’ll instead take ds and a friend karting myself at this rate
DH says I should like it or lump it and if everyone else seems to be going then it would be a shame for ds to miss out