Really all the courses are ok, the neighborhoods are perceptions in some instances that aren't as warranted as you would think. The rule is to be cautious for certain around any stranger, but there haven't been (to date) any random act of violence on a disc golf course that wasn't instigated by a person to begin with.
That being said, almost all parks within the KC area will have some traffic on them in a relatively short time span. You can go out and warm up, and generally speaking within 20-30 minutes someone will be arriving at the course, and most disc golfers are not going to say "no" when you say, I am new, and unsure of where to play, can I join.....at least I would hope not. I have met many fine people throughout the country by loitering to play with someone "local" and typically had a good time.
There is of course the league play with over 10 a week, if you can make it, that would be the best option to ensure at a specified time that you will play with locals!
Enjoy your time here!
The event on Saturday should be pretty full. Play a division that you feel comfortable with. Do you remember what you shot at Water Works? I would say if you shot 52-55 play advanced. 57-63 intermediate, and 65+ play Recreational. If you shot under 52, you may want to consider "Pro" but that is a decision only you can make. If you already have a PDGA rating, or have played in a PDGA event before, you may want to look at your round ratings to make that determination based on their guidelines.