"Nous attendons nos chers petits-enfants."
Translation:We are waiting for our dear grandchildren.
The context should readily make clear which meaning of "wait on" is intended. There are very limited contexts in which "serving someone" is going to come up.
Beyond that, the OED documents non-regional usage of "wait on" as a synonym of "wait for" spanning the last few centuries.
It need not be suggested as a usage, but it should be accepted.
I thought about it, and I don't feel any difference between the two. I would use "waiting on" and "waiting for" interchangeably, both in situations where a wait was reasonable and expected and where I was "kept waiting" unreasonably or unexpectedly.
To me "kept waiting" is the typical phrasing used to express discontent with a wait: "I had an appointment at 9 AM, but they kept me waiting until 10." (I assume "faire attendre" captures a similar sentiment.)