Bring water soakers. You may get "attacked" by other tubers. Good to have a means to respond. Old tennis shoes without socks work fine, but I'd invest in some comfortable $20 water shoes. flip flops probably won't make it all the way down the river with you and they might get stuck in the muck in some places on the side of the river when you get out. Don't try to do too long a float - particularly for the first time. Pick a 5 or so hour trip, as you (especially the kids depending on age) will also want to make a few stops along the way to get out of the river and mess around. There are many good outfitters, but we lean to the one in Sparks, because the trip from Berry Bridge to the place where Sharps takes you out of the water is about 6 hours (with a stop for lunch at Smith Falls), so timing-wise its about right. Don't miss Smith Falls. State's lease runs out in the not too distant future, and there is no assurance it will remain open to the public in the future.
If you have time - or plan a little extra time - stop by Merritt Reservoir, and if its open go see Snake River Falls just north of the reservoir (I don't know if it is open to the public or not at this time, so you'd have to look it up). And most importantly, either going or coming home find a road through the sandhills other than Hwy 20. Take 92 to Ansley, then Hwy 2 to Thedford and 83 up to Valentine. Or, if you go to Merritt on the way home, take Brownlee Road from hwy 97 south of Merritt Reservoir through Brownlee and over to Hwy 83. Its a one and a half lane wide black top road about 40 miles long or so through the heart of the sandhills. If you find yourself going through Broken Bow, Bonfire Grill in the Arrow Hotel is really good (at least we like it) - maybe a touch on the higher end price-wise, but not much (at least last time we were there several years back). I've driven through many parts of this country. Going through the middle of the sandhills remains one of my favorite drives.
Other options include going by Calamus Lake and visiting the trout hatchery on the west end. Leave kids at the hotel in Valentine if they are old enough and hit the casino just across the state line in SD, and visiting the Valentine Wildlife Refuge and see some Elk and Bison, and there are several waterfalls accessible in or from the refuge (these are on creeks feeding into the Niobrara River). Have Fun, and safe travels.
