My son will be 4 at the end of March, we went to Disney last April and he still talks about it. So I know he will have a blast and we will get to see my sister. And I know matter what we find out at the echo about the baby will never change the love I already have for her. But if we find out something bad it will bring back many fears of losing another child and I will not be doing well emotionally or at all I know it. I have been having good days and have felt that our baby is perfectly healthy this time, I've had my bad days and fears from already going throughout hope the biggest lose and pain in my life. I just have to keep believing that God knows I will not make it through a lose of another child and he would have not let me get pregnant or the pregnancy continue if it wasn't ment to be. Everything will work out how it should and I just have to keep believing that.
I'm sorry to hear about your daughter. My nephew has HLHS and it's a daily struggle for him and my family. I'm sure it'll be happy news to hear that genes generally aren't the cause of heart defects- so sending you positive thoughts that your baby will be perfectly healthy!
If you do find out some good or bad news, or go to Disney or not, you will love your baby all the same.
You don't say how old your son is - he may be too young to even conceptualize Disney.
At any rate, don't tell him you're going and then if you get good news and are going on the 26th, you can tell him the night of the 25th.
Best wishes -