AIBU to do this

[Hypermutley]

We've plans to visit NZ later this year, my bro who I'm close to and love lives in Sydney. We're visiting him and then going over to NZ for a couple of weeks. He's got 2 kids 5 and 2 - we've got none. I love them but I'm not really that patient with kids (we've got none yet but hope to next year).
Bro wants to join us on NZ trip - full 2 week road trip. I think it'll be a bit too much for us. Also we're paying nearly £4k just on flights to get there its and expensive holiday which we want to enjoy.
Bro and sis don't really go on holidays because of kids so he wants to join us so they can have one. I think its unfair on us and especially my DH. We've anyway decide on a separate car so we're not together all the time, but we will say its so we can be independent in case they wanted option not to do things - we are generally 'always on the go' on hols.
WIBU if I tell bro that its best to spend a week together but not the full two weeks? I would like to give them a break but not at the expense of our holiday.

[ItsBritneyBitch]

Sounds reasonable to me. Why don't you explain though that you want some time alone with your dh? I'm sure they will understand and probably want some alone time themselves.

[Ilikepancakes]

Could you explain that you want a romantic break with time alone, posh restaurants! Late night drinking etc. Can say you want to have a very active holiday and most of the activities (hiking/bungee jumping?!) won't be suitable for a young child and a toddler. You could let them in on your plans to start a family soon and say you'd love to holiday together when you both have kids?