Support would be the biggest thing, especially if the website needed any kind of login, payment, or user contributions. Back when we ran a website for UK schoo

Support would be the biggest thing, especially if the website needed any kind of login, payment, or user contributions. Back when we ran a website for UK schools (so, probably 50K-100K users maximum), we only answered support calls or emails during UK working hours, and still needed a 2-3 member team doing that. That was a shoestring even at the time. Nowadays just the safety aspect of running a service for children would demand something larger.