Not far enough. You are going to have to move them somewhere else at least 4 km away for at least 7 to 10 days before placing at the new location. There is no way around it. .. Unless you are fine with losing alot of lost bees to exposure and are ok allowing the old location the be lit with flying circling bees and clustering in the grass there for a week or so. If the need is to get rid of the bees from the old spot, for reasons unsaid, this is going to make that situation much worse.
I say 4 Km because I have moved yards less than that (3km) and it is surprising how many bees go back and fly around the old spot.
You could move all but 4 or 5 of the weakest hives. They would pickup the return flyers. However 300m is way too close. Those hive left behind will overflow with the large catchment and the moved hives will be severely depleted.
There is a big difference between moving a few hives and moving a yard of 25. Not only the amount of work but in the amount of bees in the air. Sorry to say, but to do this properly you are absolutely in a double move situation.
Move at dusk, loading as the sun is going down or in the very early morning before the sun comes up. If in the morning you must finish unloading with hives on the ground at the new spot at dawn before the sun crests. I prefer nights moves. At night it is just moving boxes and if anything goes wrong I have plenty hours of darkness to get sorted and resolved before the sun turns a box moving problem into a flying bee storm problem. Morning moves and watching the sunrise are nice, but there is no wiggle room for the unexpected. A simple move event can quickly become frantic chaos. Be sure to communicate with your landowners so call-outs do not show up in the middle of you handling boxes full of stinging insects. (Eg Police /lookyloos)
Hope that helps!