You should try to use rules to achieve this functionality (perform “multiple actions with one buttonclick”)
You would define a new Switch (proxy) item (ON/OFF) for each heater and then based on the state of this item, you would send the relevant commands to the Max bound items (mode & temp) using a rule.
You can also group the Switches so that you can control all of them via the Group item.
More info on:
Proxy items: Design Pattern: Proxy Item (read this first 
)
rules: http://docs.openhab.org/configuration/rules-dsl.html
Groups: http://docs.openhab.org/configuration/items.html#groups