‘Powz is going Yukon Corneilious and headin’ down to dig some diamonds, long about Memorial Weekend. There is a state park or something where you can dig all the diamonds you want.
What tools should I bring?
What anemnities should I bring?
What is the weather like down Arkansas way during late May?
What is there to do around Little Rock?
They have tools available for rent there. I don’t think you should worry about (or clutter your car by) bringing your own. You might want some Ziploc bags or a jar of some kind to bring home any finds.
As for amenities, good boots, sturdy pants you don’t mind getting dirty, a hat (wide-brimmed if you have it), and water.
You are talking about Crater of Diamonds state park outside Murfreesboro. I do hope you realize it is a two hour drive from Little Rock (about 110 miles). As for what you need, most people just walk around looking at the ground from different angles to see the small diamonds on the surface (they frequently re-plow the fields to turn the ground over). You can use hand shovels or trowels or screens to sift the dirt. You can bring your own or rent it there.
What to do in Little Rock? IAMNAC(hamber of commerce spokesperson) but, it really depends on what you like. Little Rock is a relatively small city, but it is the largest city in Arkansas, so it has amenities greater than its size would suggest. The heart of Little Rock is now along the river, with the Clinton Library at one end and the Old State House at the other. There is a relatively new rivermarket there with some nice restaurants and bars.
The state capitol building is not far away. It is pretty easy to recognize as it is a smaller replica of the US Capitol. It’s a friendly, compact city that is easy to get to know. Hope you enjoy it and good luck with the diamonds.
…and update us on your results. Finding a diamond would be very cool. (I’ve always wanted to go to Australia and find myself a fancy opal.)
I would plan on a trip to one of the quartz mines afterward. It will feel good to actually find something. You will not find a diamond. I just want to be clear on this. You will not find a diamond. You will spend the day digging in dirt and finding tiny little pieces of other shiny minerals, then going to the desk to find out that its feldspar or something. It’s not really fun.
Don’t plan on grabbing a beer afterward either. It’s a dry county.
I’ve been to the park several times. It’s a lot of fun and a good family outing. I’ve got a ring with a very small diamond that I found. Usually we find small chips that we save in a glass bottle. Keep your expectations low and you’ll be happy with whatever you find.
It’s a fun outing, but not something to plan a trip around, unless you really like to dig. Any diamonds you find will likely be tea-colored. You could also visit Hot Springs, which is sort of between LR and Crater of Diamonds. It’s more touristy, but has some funky kitsch if you like that sort of thing.
The weather in May should already be summer-like, but still prone to thunderstorms, etc.
Consecutive posts, no less. YMMV indeed. 
Three-quarters replica, to be exact. They make a big deal of telling you that on the tour.