I totally understand not having children at a wedding..

My sister in law will be getting married in July of next year. At the that time, I will have my 7 year old, 1.5 year old, and I'm currently pregnant and the new baby will be about 5 months. 
Sister in law told me this past weekend that my 7 year old was invited but the two little ones I would need to find a babysitter. Totally understandable. Glad she told me early. But all of our family that ever watches the kids will be at this wedding, lol. I don't live around my parents so they are off limits and there no way in hell I will hire someone that I don't know to come into my house to babysit them. 
I told my sister in law afterwards that I may be able to go to the actual ceremony because it won't be as long as the reception but probably won't be able to make it to the reception. I also told her that's there's a good possibility that I won't be able to come at all! She got really pissy about it and threw a fit saying that we would have to come, that she was in our wedding, and her brother has to be there and along with me. Mind you we are not in this wedding. I told her sorry but I mean when you have kids, not one but three kids it's hard to deal with finding a sitting. 
So, basically I'm stuck in a hard spot. Of course my husband and I want to go and celebrate with her but those of you with more then one kid should understand the difficulty!
I'm certainly not saying that she needs to make an exception for me because that's totally not needed because I too didn't have kids at my wedding, but she doesn't have kids so she doesn't understand that hardship!
So now she's pissed at me because I told her there's a possibility we won't be attending.. She keeps naming people to throw my children off to for the night and umm.. I don't know them. I have certain people that I allow to watch my kids, just because this world is crazy and you have no clue who people really are 
I don't know. I just feel as if I'm being shamed for taking responsibility of my children and now she's making me to feel as the bad person because my husband and I probably won't make it and now we are apparently horrible family members because we won't be there to support her.. I just wish she could see it from our point of view.
Thanks guys! We know it's early in the ball game and have tons of time to find someone. My husband and o agree if we don't personally know them on a personal level then they are not aloud to watch our children. He will not go of I can't attend. (Told him he could go, no hard feelings) but he looks at is at its his children as well and I'm apart of the family so if I can't go he will not. 🙄
As far as my parents are concerned I don't talk to them hence why we are so far away from each other lol! 
The point of this post was not because o wanted advice on how to find a sitter because that's going to be out of the question, it was the fact that his sister is pissed at me for not being able to get a sitter and attend her wedding. She is shaming me. It's all good though!
Thanks everyone!