Only time will tell.
If you did pass it on you will know eventually, and if that happens you will treat it.
This is, and has been, obviously important to you so I understand your frustration. However, it was a mistake and you're human.
As I read your question I found myself asking "why is this so important?" I wonder if you are self conscious about your cold sores, or may have been teased/treated badly because of them? Maybe you think everyone is looking at them (when you have an outbreak) and thinking badly about you? Is this why it is so important to you not to pass it on to your child? Do you feel like they will have to live through the things you feel you've had to endure because of a cold sore?
You have to let yourself off the hook!
You could spend your entire life worrying about this. Avoiding kisses, not sharing ice cream cones and other treats, and disrupting your life when you feel you may have messed up, and your child could still end up getting it from someone else anyways!
It is okay to be careful, anyone could understand that, but to beat yourself up so badly over a simple mistake? Your child was thirsty, you acted like a good parent and shared your drink, you did nothing wrong!
To actually answer your question, even though I hate to be the bearer of bad news, a cold sore can be transmitted to another even before it is visible. So it is possible to pass it along from the first tingling sensation.
HOWEVER, not everyone who is exposed to the virus will experience cold sore outbreaks! Most adults have come into contact with the HSV-1 virus and never had a cold sore. Cold sores are also EXTREMELY common, so even if you didn't pass it along, another could.
Basically, life is going to happen no matter how careful you are. I'm not telling you to rub a sore all over your childs face, but don't let it ruin your life!
Also, it is worth noting that stress causes outbreaks so maybe you were so worried about sharing your drink that you caused the outbreak after you shared with your child?
Good luck hun!