In answer to your question, robots such as you describe run on house current so when they need recharging they simply return to their docking station in the corner of the garage. Think of them as giant cell phones with legs.

Hamburgers and hotdogs with sides like potato salad and baked beans will give your barn party a rustic atmosphere.
DJ's and stereos might work for clubs and bars, but you'll find that barn parties feel far more authentic when you have live music to dance to, preferably something including a banjo. If you don't have the cash to hire a band, talk to some of the people at your barn and see if they know any musicians willing to play

hope it helps

Once you see the weeds really dying, then go find a rental store that has a power seeder. These units have a gas engine on them that drives the wheels and also drive a series of slitting blades underneath the deck. There is a compartment for the seed to go in and a guage to set the rate of delivery of that seed. Before using this machine, set your lawnmower to its lowest cutting height and mow your lawn.

Then use the power seeder the following way. Make a full set of passes across your lawn from east to west and west to east. Then go north to south and south to north in the next series of side by side passes. How you start and how you finish isn't the issue. What matters is that you cover the lawn area twice from two different directions at minimum to get as much seed into the ground as possible.

The slitting knives open the ground up and the seed falls into those slits and a trailing mat closes the slits up. This is much easier than broadcasting the seed and then covering it with a light layer of top dressing. The most important thing after the seed is in the ground is to keep it wet all the time so it will sprout and grow. Don't even think about cutting that new lawn until it is at least six inches high and then cut it down to three inches, no lower.

If you are near a farming community that has a seed store, go there to buy your seed. It will be cheaper and they often have pure seed in bulk. Tell them what you are doing and they can come up with a blend of seed suitable for your needs. Depending upon when you intend to do this and the weather that is present, you may want them to include a "nurse crop" to help your lawn get established. Nurse crops are annuals not perrenials. They grow fast, provide shade from the hot sun and are gone the next year.

Do not spray for anything after you seed or you will kill the seed. Forget the gimmicks such as dethatchers and aerators. They're mostly a "make work" project for the lawn care biz and won't do as much for you as heavy seeding. Once the lawn is up and growing use a slow release fertilizer such as 10-10-10 or 10-30-30. What you want is strong root growth, not blade growth.

As for tools, make sure you have enough hose and sprinklers to keep this lawn WET, WET, WET. I cannot stress this enough. I am not telling you to drown it but if you let the seed dry out, it won't sprout. And once it does sprout, water is essential to make it grow or it will go dormant and die on you.