But who is really hurting small businesses here?
I had a flat tyre on the school run once. Limped home - and phoned round to see where I could get it replaced - emphasising that I essentially needed to be back on the road for the afternoon school run.
Kwik Fit could do a whileUwait service - but a different brand of tyre. I preferred to stay matching. An independent mobile guy said he had the right tyre, and would be out by 11am. 11am came and went, he wasn't answering his phone.... It got to 2pm, I left a message that I couldn't wait any longer, and went to KwikFit. Cue a furious phone call thirty minutes later about how he'd apparently ordered the tyre just for me, and he was en route to my house, and how people like me kill small businesses. Will I go to an independent over-emotional tyre fitter again? Will I fuck.
If I have work to do, I'll go to a chain cafe, because I know they won't huff and puff about overstaying. If I have kids with me I'll go to a chain cafe - because I know I won't be made to feel uncomfortable about my pram taking up room. If I'm with a friend with food allergies, I'll go to a chain cafe/restaurant - because IME they are trained in dealing with allergies - and don't eyeroll when they are asked for full ingredients.
So IMO if anything is killing small cafes/businesses - it is a reputation for getting wound up to the point of being inhospitable about very minor customer inconveniences.
Frankly - once the OP cafe owner had sold a single cream tea between three - the 'spend per table' boat had already sailed - whether or not OPs parents were allowed to share the tea.
actually - I do go to one independent cafe to work - spent eight hours in there once - first four on one cup of coffee - then I got hungry and ordered a full lunch/cake/juice etc. They clocked me as an overstayer - and let me pick the music to my taste - plus brought me samples as they mixed new drinks. That is how you make money as an independent. Not* by haranguing the customer about the cost of washing an extra cup.