In law stress!

[Iltavilli]

DP has a DB (only sibling). They live 400 miles away - DH moved for uni where we met and have been together since we met there 10 or so years ago.
DBIL moved back in with in laws months ago during a house renovation which has taken far longer than planned. We are due to visit in late Aug for a family occasion. DBIL and family are still in the in laws home and when we agreed to go we all anticipated they would be in their new home, so they’re saying the house is too busy for us to stay (DBIL son staying in the room we’d usually stay in). This was dropped on us last week.
They live in a very popular seaside town, so all hotels are booked as it’s the school holidays. Plus we’re planning to take the dog so accommodation is further limited.
I suggested I stay home with the dog to make things easier, but apparently everyone is offended by the suggestion. AIBU to suggest DP goes alone?

So where do they think you’re staying? If there’s no accommodation available that accepts dogs, then you can’t go. Or DBil’s son takes the sofa with the dog. Or as you said, DP goes by himself.
Get DP to run the options past them.

Not a clue! Not relatives nearby with spare rooms.
DBIL is saying not possible to have his DS (4) in with him and partner for two nights as would upset the routine.

Take a tent? Only kidding. If it's a popular holiday spot are there any static caravan parks?

Unless nephew can go in with parents then it would be a big no from me. Sounds like they’re expecting you to kip on the floor in the lounge or similar!

Ask them for suggestions? Since they've created the problem?

I wouldn't care about offending them. Ask them what their suggestion is then as they're the ones screwing the plans up and for them to keep in mind you won't be forking out for ridiculously overpriced accommodation.

Airbnb? Put the ddog in kennels.

Thanks all! Had been made to feel my concerns were ridiculous but glad there’s agreement!

A hotel / holiday cottage (dog friendly) for the 3 nights would even approx £700 and the closest 20 miles out of town so hugely unhelpful for the event we were trying to attend. Even non dog-friendly would be not much cheaper and no closer.

To be fair PILs are fab and regularly visit. But they’re smitten with BIL ‘s son being in their home so are loathe to cause any problems for them (such as suggestion S goes in with DBIL)