I was also going to write about Now I Lay Me Down to Sleep.
Sadly, I had a friend go through this in May, and she did this and is very happy that she did. They do an amazing job and my friend has something special for her son
But, as for a trip to Disney, I have to agree with No. My friend is still not cleared for work as mentally she is not doing very well, and it has been 5 months. She can still not be around babies and families. I think a trip to Disney, although very exciting, would push her over the edge.
My SIL is also going though this, and same thing. She is just not doing well and her baby passed on in July. She has a DS2 and I cannot see them taking a trip anytime soon. It is work for her to just get together with family.
Please just be there for your SIL, but don't push her. It will be a long road for her and her DH.
She is lucky to have someone like you who wants to help, but there are some things they have to do on there own, and you cannot push them (I am not saying you would, I am just saying that anything big right now might be too much for them).
Take care and my thoughts and prayers are with them!!

And you, since you will also be losing a niece or nephew.
Good luck!!