Gordy, has your wife been on the medication long enough to be stable on it?
The mention of mums accompanying sons on those much-vaunted trips to Thailand had to make me grin.
Sounds like you've been fighting an uphill battle for some time. Hopefully, the medication will help your wife with some of her upset. Truthfully, I wouldn't put off you going on your trip with your mum because of her. I'd hope your wife would eventually see that it was a sign of what a good guy you are.
My next-door neighbour's oldest son died recently. Her married (with two children) son went to the west coast with her for two weeks to settle his brother's estate, and to help his mum say good-bye to her son's friend out there. I know that most of us respected him very much for taking that time to be with his mother, and to support her at this very difficult time.
Interestingly, in terms of katya's comments, there is also a surviving single/no children, brother. He didn't go along with them.