I don't know what will happen on United, but I bet the TG flight attendants will play with and watch your child while you eat and use the bathroom. I've had flight attendants do this on LH, OZ, CX and TG. In all cases, the flight attendants volunteered.

I did this on both airlines I worked for. Sometimes we'd take the baby just to give the parents a break (and the kid was willing and cute ) But not during a meal service when all hands had to be on deck so time your rest stops accordingly.

On the Asian airlines, they have really really big crews (like an army!) so they might have someone available to do this even during a service. Not sure but more likely.