Their first snow can be a serious problem. If they take to the trees, they won't come down. My first serious snow I sprinkled hay on the snow to make a runway for them to land on.
The run is a bit small. Guineas need a lot more room than chickens need. The coop is about right for 10 adult guineas although I did slowly squeeze 15 into My Coop.
Five month old guineas should be okay without supplemental heat. Your local person should be able to sex 5 month old guineas by...