Yes, it can be tricky knowing when to advise and when to wait for questions. I have learned to keep still a lot of the time.
And sometimes I fail to express curiosity and interest, in the spirit of not being nosy. Clearly SRS means only to be helpful so it's hard to get prickly.

Anyway, on the big bag of change. Another option, if you ever use self-checkout when going thru a big store with just a few items, you can feed in currency and coin just as you can a plastic payment card. So you might set out to use the coin up that way. The machine doesn't get annoyed if you feed in 40 quarters instead of a tenner.

If you're morally opposed to self-check, just include some of the loot in your payment to the cashier. Lots of times they can even accept 'multiple tender' where you can pay part with a card or check, part with currency.