Maccat,
I recommend you re-define success for both of them. At this age I would not define success as win vs loss. The reason I say this is because at this young of an age there are too many variables that cause a kid to win or lose. Most of them are due to personality, aggressiveness, etc and do not involve a lot of good wrestling technique.
If you have them focus on things like trying different moves, giving their best effort, practicing hard, etc. then as they get older and are more mature it is easier for them to orry about winning and losing. An example is have them focus on trying the takedown they were taught in practice or whatever move they were taught that week. Emphasize that. This will help them focus on practice and getting good at their technique. It will also keep it interesting and challenging for them.
Most of all....make sure they are having fun and learning to love wrestling and the thrill of competition.
Hope this helps.
Shawn Budke