Determining if a dog has Separation Anxiety

I'm pretty sure one of our dogs suffers from dog separation anxiety. Either that or he is just a lunatic. First, he's a spring spaniel /lab mix. He's almost 8 years old and hasn't settled down. He's a male and we thought getting him fixed would help take some wind out of his sails. Yeah, that was 6 years ago and he's still going strong. His name is Scout. He constantly whines when inside, especially if the kids are around. The problem is that he's an 80 pound goofball while our kids are 4 years old and 17 months. He's too goofy to play with them. Add in the fact that he has randomly used the bathroom in the house when we've let him roam around and you can see why he doesn't get a lot of time out of the laundry area. The whining is high pitched and hard to take for extended periods of time. I'm trying to use some of the Sit Stay Fetch methods and they slowly seem to be working. I'll keep everyone updated on how it goes.