Release week, summer holidays, and 45 minutes between his camp van and my getting home

Son is 9. Camp drops him at our building at 5.15, and this week I can't be home before 6. More like 6.30 when testing runs over, which it will. Family nearby can help sometimes, but not every day. He has a key, knows the neighbours, and swears he'll just read. Part of me thinks 45 minutes alone at 9 is fine. The other part has already pictured him making noodles on the gas 😅 Has anyone done this around this age? What rules did you set?