I thought I would reply because I did just leave my 10 year old at home with my parents (and husband when he was actually home from work...) while I took my other kids and nephew to my in-laws summer home for the week. Definitely different circumstances - my son was still playing baseball (which had to be a priority) so he couldn't come. I will say I was very pleased that my son understood his commitment and actually didn't fuss about not being able to go.
Anyhow, I have never dealt with bipolar issues so I cannot speak from experience there, but it would seem to me that all kids need to learn that sometimes it just isn't possible for everyone to do everything together. If we "wait" on everyone to be available when we have more than one kid, we might never get to do anything. Without knowing absolutely everything that has been going on with your son it is hard to say exactly what I would do in your place, but I do think what was suggested above are good options. Go on the trip as it cannot be rescheduled and plan to either bring something special back and / or do something special with just him when time permits.
As parents, we have to pay attention to all of our kids needs. There are circumstances where we need to adjust our lives for certain needs of one child and at the same time we do need to be careful we don't adjust all of the time. I think as long as we make it clear that we do indeed love each and everyone of them and show them often that we value them, we can make the hard decisions from time to time to either do something without one of them, adjust plans, or even make them do something for the good of the family.
It sure can be tough being a parent and making the hard decisions, but God knew what He was doing when He gave you the kids He did.
Blessings,
Wendi
