What do I advise brother and SIL to bring on hols with them with 4 month old nephew?

[Miti]

My brother will be coming to stay for 2 weeks with his wife and young (4 mo) son. I have said they are welcome to use the few things we have collected for our coming baby (due early Dec).
I've suggested to my sil to bring her baby's familiar blanket or rug to help settle him into the new environment. I've told her we only have a travel cot which I'm sure will look very foreign to him but she seems obsessed with the amount to bring.
We have a car seat that he could use but they are bringing their own and I have said that the paths around here are not fantastic for non ATP's and they could use our baby carrier but they are bringing their pram anyway.
I suggested that I research the foods available here for him (he has just started to be weaned onto solids) but she wants to prepare his stuff herself.
How do I encourage her to just chill out, bring essentials only to have a trouble free and most of all relaxing break away?

Miti, don't worry about it, she'll ask if she needs to borrow stuff. Anyway when she realises how much she's got to pack I'm sure she'll change her mind! It does seem a bit daft to fly with a car seat if you've got one she can borrow. Is it all going to fit in the car at your end?

Miti please don't take this personally, but I'm a 1st time new mum and when my son was 4 months old I too took all my own stuff, pram, travel cot everything when ever I stayed anywhere etc. Also at the weaning stage I too prepared all his own food as I found it very simple to prepare etc. Although I was a new mum I found this time most rewarding as well as hard work. But I did thoroughly enjoy it too...Maybe your SIL is just enjoying it all too and doesn't find it a hardship, slogg or stressful thing to do.....I can understand you want to help and make her break away as relaxed as possible but what you may find stressful she may not and vice versa. So just let her do her own thing and just be there ready with suggestions when she asks for them...after all you will know your own area, town etc alot better than she will...ie baby change facilites when out & about, nice parks for a walk if she wants, child friendly eating places so you can all enjoy yourselves while her son has he's food prepared by mum etc etc etc.

P.s YOU ENJOY THE TIME WITH THEM TOO!! THATS ALSO IMPORTANT!! (You are pregnant after all)