Not to sound like a t**t but we've gone the other way. I couldn't spend for a long time as it just seemed weirdly profligate. I'm not a miser but I am a saver now. I enjoy being able to help family out and to treat people I love a bit more. I have bought myself clothes from better labels, nothing major designer but high end highstreet.
As I don't really go anywhere bar doing nursery drop offs and walking the dog I've stopped that now. It's made me appreciate better quality but I'm enjoying getting quality stuff on vinted for a fraction of the price and selling my excess/wrong sized stuff there too, which basically makes new purchases free. I feel better about not adding to the tonnes of clothes going to landfill too.
I still shop in Aldi because I can't justify spending more on essentially the same things but also because I like the reduced choice. Enormous supermarkets with 800 different cereals or crisp flavours and entire aisles of sauces are so unnecessary and quite stressful. I occasionally get a waitrose delivery when I want to stock up on some things aldi doesn't do and add an odd treat in which I'll thoroughly enjoy, because it's a treat. Otherwise quick simple meals from real ingredients. If you've got eggs, beans & lentils, veg, fruit, yogurt, pasta, rice & porridge oats you can eat well.
We've always done loads of free days out, beach, country walks, park and playdates in the garden. If your son wants to have or do something that costs add it to the birthday or Christmas list and save up. Waiting for something like that adds to its appeal, getting what you want whenever makes special things much less special. The same for yourself when choosing to do things with friends, accept something you really want to do once in a while so it's affordable and try to do cheap or free meet ups otherwise.
When really struggling once I got a second job as front of house at a theatre because it was a bit of extra cash and I got to watch plays for free. I also met loads of lovely, creative people and enjoyed the social aspect, plus it helped longer term with career connections. Maybe your son could think of something he enjoys doing and find potential part time employment in it? Much, much more for him to gain than just the pocket money that will help out in the short term.
The world's become much more consumerist in my lifetime. DH and I were recently discussing how we could remember exact outfits or toys from childhood because we just didn't have much stuff then. There are lovely memories attached to things because they were a constant amongst few items for a long time. How many of today's kids will be gifted that when we seems to buy new clothes and gadgets at such an alarming rate? Slow living is a positive idea that might be worth looking into, although it really means what my 80s 90s childhood and youth looked like.
As long as you're not in absolute poverty you might find you can enjoy life from this perspective more than you thought you would. I hope so anyway.