you should be able to but you should be careful of your gourmais as they can nip the fins of your betta . Our gourmais are ok and dont nip our bettas fins so it could be ok.
I would not mix a male betta with gourami. I have heard nothing but bad stories about gourami and betta's fighting. They are both top-level fish and both are teritorial and got good biting power, that just adds up to trouble and dead fish IMO.