I've been looking for a generator to power a small window AC unit, a few things to keep the kids entertained, and the fridge/freezer once a day or so keep it cold during an emergency. I found this Coleman Powermate 3250 for $100. This is an older model, so I have not found to many reviews (I don't have a model #). Should I fo?

You don't indicate how big of an AC unit.  That said, 3250W should be able to power up almost all window units.   I know that there have been sales of the highly rated Champions at same wattage range for $279. That's something to think about.

That said, if you can do a cold pull startup test and run the unit under load (I use electric heaters - 1500W).  If the engine starts fine, idles fine, and can handle full load without dying or sounding strange, its probably not a bad deal for $100.  Coleman's are really loud (think bad lawnmower).  I'd recommend hearing protection to use and look to build a enclosure and/or add a car muffler to lower the db or face hearing loss).  You can take a look at the oil and pull the spark plug to also get a understanding of how it's been maintained.

If you buy, change out oil, run, change again.  And fill and run in new gas (preferably ethanol free with your favorite additive stabilizer).  Maybe replace/regap your spark.

I have a powermate from 1999 that is 2500 watt
it sat one time for over 5 years, never started it, and it took 6 pulls to fire it up. 

I've used it several times to run my fridge, 5000 btu a/c and the tv.
just run the fridge and the a/c at full blast, start one at a time and don't let them cycle on and off, do it manually so they don't kick in at the same time and you'll be fine.

$100 is good price for a little back up power
I paid 4 hours of light labor for mine, cleaned out a buddy's garage. he bought it new, I got it in 2002

yes mine is loud, a bigger muffler will NOT help with that, check out youtube bunch of video's with DB meters, you get about 2 DB's less with a car muffler because
the noise is actually the engine  and genset itself, not the exhaust.

only way to get a quiet generator is buy one that's quiet

I picked up a powermate 8kw unit for next to nothing.  It's been unbelievably reliable. Haven't used it to much. Sat for a year, fired right up. Now she gets fired up about once every 6 months just to run it. 

As mentioned the champion generator has been available on sale and what not, should be able to find under 300.  Saw some being clown out for 200 or so. 

I would not have an issue with that one probably.

1k watts will generally run a 5k btu window unit, sometimes you need to play games like getting the fan spun up then kicking on the compressor but not a big deal.

Test that one to see if it works.

Playing on youtube will show you the noise and ways to try to deal with it.

I pretty much plan on just running a genny during the day.  Before I go to bed the window ac will be used to cool things off.

At night, things secured and locked down.  I have dogs in the yard, so no major worries about someone wandering off with stuff without me hearing about it.

People have managed to use that 2 cycle 900 watt genny from harbor freight to run a window ac unit, tricks required but it did it without major issue and once you know how to do it the tricks are not a big deal.