Babysitting

Is babysitting hard? My mom and grandma are going on a trip to their home country and my auntie and uncle are going to be working so i volunteered to help them out and babysit their 3 kids. The oldest is 10, the middle is 9, and the youngest is 3.  I am very good with kids and i dont think it is as hard to care for them? I have done it before with adult supervision before when i was around 12? I am now 17 and will be caring for them throughout the day while their parents are working. I have heard that baby sitting is hard, what are your opinions about babysitting? Can you give me any advice on what to do if they're bored or if they'd want to go out and play?