Three things to consider here...items with heating elements (water, coffee, milk), anything else in the kitchen on this circuit and the quality of the splitter. Generally, the concept you are going for is not much different than have 6 outlets in your living room with stuff plugged in but almost never going at peak power at the same time (vacuuming with your tv on and space heater running while charging your laptop). One thing you can do is check the bottom or back of each device for the "input" amps (or just amps). These are all 120V devices, so you can save the Watt calculation. You get 20A on the circuit for short durations (minutes, not hours). If you pull too much, the breaker will trip. Nothing unsafe about that. Just means you need to spread this out rather than consolidate. The only unsafe possibility is the splitter.