Hi there....I know you started radiation now...congrats to your kiddos for weddings.
Like others have said...everyone reacts differently. Most say that stuff doesn't get affected till week 4....but there are a lucky few...like me, lol....who get "fun things" started at about 4th treatment. Everyone is different....and sometimes no matter how hard you try...you need the peg and have no choice.
You can't always control what you will experience and what you wont. Just try your best and I am sure they will understand.
I hope you get to go. I am not sure about traveling, but I know for me, the last 2 weeks of radiation, I could barely tolerate the car ride to treatments, otherwise was on the couch the rest of the day...but I was having issues with peg tube and not getting enough fluids or nourishment, so it may have been different if I was able to get adequate calories and nutrients in.
Hope you get to make it, if not...they will understand, they are your children. Maybe make a recording ahead of time just in case that can be played if you aren't able to be there for them. But I would think having something that exciting will give you something to push for, but like i said, you can't always control what happens to you, no matter what you do! I will keep you in my thoughts and hope you get to go!