This aquarium is located inside the Silverton Casino and it's free. They have stingray feedings and the mermaid show! (please check their schedule before you go)
Silverton Aquarium with Mermaids
One of the best children's museums with many interesting exhibits and engaging activities for kids all ages.
DISCOVERY Children's Museum Las Vegas
This place is a huge trampoline park for kids. They offer ninja obstacle courses, climbing walls and laser tag. If you have younger kids, I'd recommend going there earlier to avoid the bigger kid crowds.
FlipNOut Xtreme - Trampoline Adventure Park
They have countless activities and illusions that will keep your kids entertained for hours. Kids under 4 are free!!