Should I decline party if we can't arrive in time for the start?

[Johnny5isAlive]

DS1 is invited to a 6th party at local Hollywood Bowl. But we can't get there until 20 mins-ish into the party. Obviously this is costing the parents money so don't want to take the piss.
Should I decline and let another child get their money's worth? Or AIBU to accept the invite with apologies that we would be late? They aren't close friends but DS1 would be disappointed if he couldn't make it

I would decline

Will it be 20 or more like 30 or 45 min if traffic is bad?

I think decline but tell the parent why, thus giving them the chance to say "don't worry about missing 20 minutes, that's fine". And if they don't say it, it's obviously not fine and you made the right call.

I would speak to the parent. 20 minutes isn't long. Most people tend to be late to parties anyway (in my experience!) so I can't see it would be a problem, it wouldn't bother me if I was party parent.

If decline and tell the mother why. If she says it's still ok then go

I would be concerned that the mum would take the 20 minute thing as you trying to refuse politely and wouldn't bother to say 'oh 20 minutes is nothing, don't worry!' for fear of putting you in an awkward position. So I would make it clear you were actually interested in coming if the late show is OK with her.

Depends if they're going to start bowling straight away. Once the games start you can't just add another person half way through and the machine won't let you skip a person and the games are one after another and take a while.

That's if it's bowling like

YOU can't join in late if it'e bowling. The score screens are programmed with the name of each child at the beginning of the game.

Very rude.

Yes, that's a good point. If they're eating first then it's possible, else it wouldn't work.
I'll explain to the mum. Thanks all

They could put his name on the board and get another child/parent to bowl his turns until he's there. No biggy. We had a bowling party and (as I said earlier) we had late arrivals due to terrible traffic that day and it didn't spoil dd's party.. she still got presents after all

I'd ring up and explain that we couldn't get there in time and would be about 20 minutes late. I expect the Mum won't mind. Could your child not get a lift from somebody else going to the party or find some way of getting him there on time.

Never been to Hollywood bowl but at Ten Pin you are supposed to arrive 15-20 minutes before bowling time to sort out shoes etc.
Its usually more like 25-30 if it's busy. By the time a bunch of excited 5 and 6 year olds get sorted you might be just in time to start bowling.
Obviously tell the party hosts first though.