I don't know how SFEG is, but I would definately go to Lakeside Amusement park while you are there. I passed through that area a little over a year ago, and chose to visit Lakeside instead of SFEG. I don't regret it one bit.
I also reccommend Woody's Wood Fired Pizzas as a place to eat while in Denver.
It's the most fun in the park when your laughing in the dark.