I have guineas with chickens but I have always introduced juvvy guineas in with mixed ages of chickens and turkeys. I have never had any losses as a result. I do find that the guineas consider themselves top dogs, even with the turkeys. Nothing like seeing a male guinea trying to break up a tom fight, lol.
I think it is key to raise your young guineas with other birds, it is the only way they will really tolerate them in close quarters. My last groups of guineas were raises with quail, pheasant, and chickens from hatching. I have to do that due to space and because of the extended amount of time that they all have to share a coop in the winter. This winter has been mild, hasn't gotten too much colder than 0 so they have been getting some play time outside.
Last winter, it was -30 and colder by this time, resulting in the birds being cooped up from mid-November until mid-April.