C.H.
I'd do what Heather B. said.
To make a long story short. What I did. I took my son (2 or 3 yrs. at the time) w/ me, when I had to put my elderly (very old) dog to sleep. Because her whole body was shutting down. Anyhow, it helped my son out (taking him w/ me - when she was put to sleep). He wasn't traumatized or anything. I explained what was going. From time to time, he'll still say he misses her. But I remind him. That we'll see her in heaven some day. And that she's up there in heaven playing w/ Bailey, Klondike, Bingo & etc.
Anyhow, hope this helps.
C.