How can I make a map?

I have a tradition that I have done ever since 3rd grade, it's where a have this big all girls backyard camp, and all the girls in my grade who go to my school and a couple other girls are coming. Last year (5th grade) nobody would listen to where everything is, and when they were supposed to go to water events, they end up going into the creek or something (my backyard is really big, and my house is small lol, Not small small just not a mansion or anything) because they didn't know where the event was. One time it was time for roasting marsh-mellows for group yellow and a few girls got mixed up with group green for free time at the neighborhood park, and everything just got out of control because girls would say "We already did this!" "No, we didn't!" "I didn't get free time!" and stuff like that. I figured a map would solve that problem this year, and I tried making one on sumo paint. It was really hard though, because I would have to go through all this work just for 1 little thing. Is there any easy ways to make a map, like sort of professional looking. Not like the Disney World map, but better than Paintbrush on the mac.