from what you have shared i think tying into the main house electricity is probably the cheapest and easiest solution.
running a generator constantly is not cheap. both in fuel and maintenance. and it can just be a pain,logistically
solar to run ac is doable, but take a sizeable array of panels, and a decent inverter. sounds like you are in the shade so would need extension cords to get the panels out in the sun. which can be doable if the sun is not too far away
i think a proper line extension or a quality custom extension cord could be the best approach. based on what you have shared. with the caveat that not knowing what "really long" means could change it all. although anless your 2 acres is a real funky long skiny shape. you should be able to reach most of the property with 500feet of cord. a 2.5 acre square is only 330 feet on a side and less than 500 feet across the diagonal
be mindful that with a "really long extension cord" you have to deal with voltage drop. even as is wisely recommended above you use proper wire and basically install an outlet out by your spot. the problem with voltage drop is when running a larger load, especially a motor. like in an AC or fridge. the lower volts will cause the unit to draw more amps and that can be damaging to the motor if it will even run. voltage drop is less of an issue with things like lights.
there are lots of online tools and calculators to help figure voltage drop. i like and use this one
https://www.calculator.net/voltage-drop-calculator.html
depending on how far "really long" is for you. it should not be too cost prohibitive.
i would make sure that under load i still had 110 volts at the appliance. a small window AC draws about 5 amps and a big window unit that still plugs into a regular wall outlet draws around 10 amps. if your house voltage actually measures 120 volts (it varies from place to place) you could run a 500 foot extension with 10 gauge wire and still have 110 volts with a big ac pulling 10 amps.
some one mentioned codes and laws, so i will add, most states require permits to install an electric line. it would not be a bad idea, but if you are trying to avoid being noticed so you dont have to deal with code inspectors and such. pulling a permit might be a can of worms. you could use the right size wire based on calculated voltage drop. MAKE SURE you use outdoor rated wire it will have a thicker tougher outer coating to prevent wearing through and exposing live wires and it will resit moister and UV light. light will degrade cheap romex (indoor) wire insulation in time. and water will slowly soak in through the insulatsion and cause moister problems inside the indoor rated wire as well. but then wire it up as an extension cord with plugs on both ends. that way you could roll it up and take it with you it would not be the "right" way to do it. but it would be a lot better than buying several cords at home depot and stringing them out.
even if you run the wire in conduit, you dont want to use the indoor rated "romex" almost all the code books now prohibit using indoor rated wire in conduit as moister will get in the conduit and if the wire is nt rated to handle it you have the same problems with moisture