I would choose the Trampoline, it is the best thing I have purchased for the girls (although Santa got all the credit )
I don't think pets should ever been given as a gift. I do think all kids should have pets though. I adopted a dog when my girls were 18 months and nearly 3. We went to the shelter, looked at dogs and met the dog we thought suited us. We then had to go back another day to adopt her.
The kids were able to help get everything ready for the dogs arrival (choosing all of her bedding, food, toys, grooming things, collars etc) and learn exactly what was expected of them how they should look after our new dog before the dog came home.
On the adoption day they knew what to do and I think it made everything run so smoothly. We adopted a 1 year old dog so we knew what we were getting so there were no bad behaviour surprises. Yes we missed out on puppy cuteness but we also didnt have to deal with toilet training, biting, jumping and scratching so were are ok with that!