why now?

Yesterday afternoon after 2 months of being fine, our 6 yr old mixed breed dog started having diarrhea and throwing up. He was fine for a little while and decided to go in the basement and sleep on the cold cement floor since it was quite warm yesterday. I am sure not feeling well, the cold floor felt really good. well he didnt whine or anything to go out so I figured he was fine. My dh was gone golfing with his dad and I was taking care of the boys. I got them ready for bed late last night around 930 and dh had just gotten home, the boys went to bed and I went down to finish the laundry. well the poor dog had gone twice on the floor, so my dh came down to clean it up and noticed it was bloody! Its wierd because Buddy is acting ok, not lethargic or anything. Jason(dh) decided to take him in first thing this morning to have them look at him and run some tests. I really hope they can take care of him and make him better, I would hate to put him down. He is a great dog, wonderful with the boys and they love him, plus he is a good guard dog, barking at anybody he doesnt know before they even get to the door. Especially with my dh getting ready to leave I want the dog around! How can I explain what is going on to a 4 and 2 yr old? If Buddy dies, and my dh leaves on Thursday for a year, are they gonna be totally confused? I dont want them to think because daddy isnt here that something happened to him too. I am sitting here just waiting to hear from Jason. I will post an update later.