Looking For The Perfect Pet?

I am looking for a dog for my granddaughter. She is 4 and full of energy. We live in Illinois and it is very hot in summer and cold in the winter. We travel 5 hours away once a month and the dog would have to travel well. I want a small dog, but yet I want it to be tough and playful. Any suggestions would be great, was looking at pug dogs and they were perfect except it says they are not good in extreme weather.