My Father-in-law gave me a good answer for that question. He said to tell them that whatever they need will be in Heaven for them. So if God decides that they need Jake, then he'll be there. That comforted them some.
-Kevin
Creed's (a little boy of about 10) favorite hunting dog died. Creed was all upset and asked Christy (she was the school teacher/missionary) if dogs went to heaven. She replied sure. Well, a couple of days later, Creed put his head down on his desk and began to wail. Christy asked him what the trouble was. Well, Creed's dog hadn't gone to heaven yet.
"How do you know, Creed?" Christy asked. (paraphasing)
Creed replied that he didn't believe Christy about the heaven part, so when he buried the dog, he buried him with his tail sticking out of the "buryin' hole." On the way to school, Creed checked the grave and found the tail still sticking out of the grave.
As soon as school was out, Christy sent word to the Allens to bury the dog correctly... Next day, no tail, and one happy Creed.