Need Suggestions in Las Vegas...

I will take vacation to Las Vegas for 4 days (3 nights). We may walk thought some places in Las Vegas and may take 1 day to Grand Canyong then.

My son is 15 years old. So, need some suggestions where there are some good places/programs for the kid.

Also, we will rent a car but friend told us not necessary to rent a car --not sure why.

Thanks in advance!