Might break down when meeting niece/secret miscarriage

So my niece on my husbands side of the family (from Virginia) is coming to the west coast with mama and this will be the first time I'll get to meet her (8 months old).
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However, I have a secret. My husband and I are conservative (as are our families) and we were "waiting until marriage" but we slipped up and became unintentionally pregnant December 2013 (we were engaged before we found out) we kept it a secret and just as we were accepting it's and ready to tell the family I miscarried at 11 weeks. No one but our closest friend and my boss at the time knows about it.
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Anyway I've mostly gotten over it and was just suddenly emotional when I realized my due date anniversary will pass during the visit. I realized it'll be excruciating hearing about "the first grandchild/great grandchild" in the family, when my husbands grandmother-basically his mother and who raised him-would have had a great grandchild before and he/she would have been 2 this weekend had we carried to term.
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I just don't know what to do? What if I break down? I will be staying in their house, and they're usually super understanding even with their conservativism (many in the family decided to get pregnant pre-marriage and they never bad mouth them) but I don't think my husband wants everyone to know and I don't want that either. I have a possibility of never being able to carry to term, so I figured I could just blame that since those emotions will probably be flowing too, so it wouldn't be a lie.
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I just don't know what to do. I'm so excited to meet this new baby and don't want to ruin it with all my sad emotions.