Hey PB ,
It sounds like your mother is a very understanding person. I'd value that to the grave.. but it also sounds like the job isn't something that you'll find easily.

Personally, I'd lean towards the promising job given the economy situation. Job losses are happening left and right. Skilled, hard working people are losing their jobs and you can be sure they're looking for a replacement just as hard as anyone else.

Postpone your trip or have a vacation @ home. Get out and enjoy the summer with your mother while enjoying your new job at the same time. You can butter both sides of the bread and have a double decker sandwich... they're satisfying.

I'm sure she'll understand and be proud to have such a great child.
Best of Luck,
Bob.