Do I have the right to be pissed off?8

Okay. Long post and off topic a bit but I feel comfortable coming to you guys for advice.

So yesterday my husband, baby and I were planning on going to town to get groceries which is an hour drive. My husband gets off work at 2:30 PM and we were going to try and leave our house by 3 pm because we ordered walmart pick up groceries and needed to go to a few other stores.

My sister texts me asking if I can pick her children up from school at 3:30 since the bus doesnt go all the way out to their house and her and her boyfriend work. I told her that wouldnt be an issue since we will be going past their school around that time along the way so we would be able to drop them off. I asked her which kids since the oldest just got her driver's license and there is 3 kids (16 year old, 11 year old and 9 year old ) she said all three. I told her i can't fit all three because I only have room in my car for two kids (I drive a fusion and it only seats 5 total)

She texted me back saying no big deal she will just ask her oldest daughter to hang at a friends house until she gets off work and she can get her from there

I said okay. I will pick the kids up.

3:30 pm my husband, baby and I get to the school to get the kids and all three of her kids are sitting there waiting for me.

I am a bit shocked because I dont have room for all of them. I stop and they all get in. (16 year old has the 11 year old on her lap)

Obviously I am not going to leave one of the kids stranged at school so I did end up driving illegally back to their house 8 miles away and drop them off at home. I drove a bit under the speed limit because I was uncomfortable with the situation.

I drop them off and call my sister to see why she didnt let me know in advance all three of the kids were waiting for me, and she could have at least let me know ahead of time and I was just frustrated . She didn't answer the phone and never called me back.

I am pretty annoyed and pissed. I feel she kind of took advantage of me. I keep thinking what if I would have gotten into an accident??? What if I got pulled over?

Am I being over dramatic?

I am tempted to text her "next time you have me break the law, let me know it advance. Thanks." Since she never called me back.

Input?

Update

I am not going to text her that message. You guys are right. I do not want to start a fight. I just know how my sister can be and I am sure she told them all to ride with me, and its just her failed communication to me knowing I would not be comfortable having kids ride on each others lap. This is stuff my parents did to us as kids but the laws were not as strict back then. I can't imagine what kind of ticket that would have got me, or if that would fall under child endangerment? not sure...