Help!

Mary • TTC newbie, runner, and vegetarian with irregular cycles and period duration
I posted on the June board but thought of get your input too: my SIL lost her baby and you know I had those huge plans to announce at my party during the holidays, announce to literally everyone at once. I found out recently she and her family are coming to the party but she's feeling really upset around people who are pregnant. It's been a strenuous year with her and my brother (before her miscarriage) and things are finally feeling like they are getting better with my family. I really want to respect her feelings and not let her walk into a huge trigger. I also really want my family to continue staying close. At the same time if I tell her beforehand I feel like she won't go to the party and I expect she'll have a difficult holiday with everyone talking about it or she won't go at all. So I could wait until after Christmas but I've planned all gifts around this announcement and we've been so excited about the announcement. I'm having trouble hiding it too. I want to celebrate this with everyone but don't want to neglect others feelings. My family is my #1, and is a big reason why I'm feeling ready for this baby. I don't know what to do but know it'll have to come up sometime. Ideas?