"'Waiting on' somebody" has become more widely spoken in recent years because of the influence of hip-hop slang and bad grammar on proper English, but it's grammatically incorrect, unless referring to a waiter at a restaurant "waiting on a customer." The proper grammar in the other context is "'waiting for' somebody."
After the phrase čekají na, "are waiting for," the name takes the accusative case. Here's a chart of all the cases for the Czech name. https://en.m.wiktionary.org/wiki/Kate%C5%99ina#Declension