I think it is time for a talk. I'd like to set up some kind of bi-weekly thing for the boys. Something that they can count on happening that's not hinged on the grown ups hanging out. I enjoy having her son over at our place. I just need to emphasize to my friend that it's important that she follows through with having the boys see each other if that's what they're expecting. The last minute disappointment can't be much fun for either of them.
Everything will be ok in the end. If it's not ok it's not the end.