Beekeeper here! 300m should be ok, definitely far enough that you don't have to worry about foragers "drifting" into other hives. How many hives are you both planning on keeping? There's only so much forage to go around, especially if you both are planning on keeping 40+ hives for example.
A nearby-ish water source is a good idea to have (natural is fine, they need the minerals), and if the different hives mingle there it's totally fine. Let me know if you have more questions!
