Hi Dee,
I'm a kid. 24 years old, and my parents are a lot like you - frugal, careful, and generous when it comes to the kids! This is a tricky thing.
My mom won't buy herself a $200 jacket, but she'll buy me one. Yes, she can afford it, and it makes her happy to buy me things once in a while. But it creates habits in me: I know that 50% of the time, if I say "I really wish I had a leather jacket. Oh well, can't afford one right now" she will derive great pleasure in buying it for me. Expand this example, and perhaps your son is not jumping to pay for his own wedding, because he figures mom would just love to - especially if mom has a habit of being generous where the kids are concerned. If my mom won't buy me the jacket, I'll gladly do without - but I'm not going to say no if she offers!
I realize your situation is different, but I was hoping to shed some light on the matter from a "spoiled" kid's point of view. Here are this that help me stay grounded:
-my mom draws the line. She won't pay money for things all the time. Only when SHE wants to. Sometimes she says yes, sometimes she says no.
-my mom supports me in so many other ways. She won't give me handouts of money, but she'll bake me a pie or make sure I'm comfortable when I visit. There are so many ways to show love and support - perhaps for you that could mean offering to help DIY aspects of the wedding to cut costs? Are you crafty? :)
-my mom lectures me about money and the importance of saving. I hate it, but it sinks in. Sorta.
-watching Gail Vaz Oxlade's shows (til debt do us part, princess, and money moron) taught me so much about money, and helped me see how badly I never want to be in debt!! Watch the show when your son is over :)
-I echo the sentiment about maintaining a good relationship wih your future DIL. if your son has to choose between you and her, do the math... She will likely be in his life longer and have a greater affect on his day to day living. Be careful there, and make it so he doesn't have to choose. Try to respect her, and realize that she is a victim of the wedding industry :(
-If you feel selfish about not paying for their wedding, think about it this way instead: it is very generous of you to not make them pay for your old age expenses! You're thinking of their future, and if they can't see it that way now, maybe they will one day.
Good luck, Dee! You sound like a very caring mamma, and of course you want the best for your child. I think a little tough love will earn you respect over time. I love when my mom pays for things, and I may do a teeny grumble when she says no sometimes, but it makes me respect her and admire her values. It's not yes yes yes all the time. She weighs things carefully. I tried asking her if she and dad had ever considered contributing to my future wedding, and she replied "Your dad and I paid for our wedding..." So maybe remind your son that any expectation he had were concocted by his own mind, and you had made no promises. Good luck!!! It's hard being a mom, and you want your child to grow up with things you never had, but also not be a brat. You can do it! Read stuff by Gail Vaz Oxlade. She gets it.
**Please don't think I'm a spoiled brat! :) I help my parents in many ways, spoil them on bdays and Xmas, and call and visit often. I love them and help on their farm, and I realize they are very generous and I am very privileged. It's a slippery slope, though! Parents gotta be firm.
Sorry this was so long!