Unfortunately, a device needs to have a cellular modem to be able to grab mobile data. This means you won't be using your tablet.
The thing with mobile data is, it's not that cheap and usually if you want it by itself, you have to have the right device.
If all you're wanting is Facebook, email and a temporary hotspot for basic web browsing... my first question would be what (if any) mobile provider are you using currently, and what are you paying per month for that non-data service?
T-Mobile based providers are going to have the cheapest mobile data available either indirectly coupled with a talk and text plan through an MVNO like US Mobile, or a stand-alone mobile data only device through T-Mobile prepaid directly. Either way, figure around $10/GB for lighter usage and at least $20 a month. So long as you don't stream anything or do heavy updates to a desktop, a couple GB of data a month would probably be plenty. It gets a bit more pricey and complicated if we have to go AT&T or Verizon.
If you go smartphone and can go US Mobile (T-Mobile without roaming coverage), a nice and solid used/refurb T-Mo locked Lumia 435 can be picked up for under $25, and the data prices past 1GB/month would fall in line with T-Mobile prepaid for data only plans, with the talk and text end probably falling closely in line with what you may already be paying. The nice thing about US Mobile is that they technically aren't too picky about selling plans with data only for phones. They're one of very very few MVNOs who do, though.
Stand alone WiFi hotspot devices will run you closer toward $30-50 used, and you'll likely have to commit to $35/month or higher rates for around 3GB of data. TOAST.net is a good option for this route for AT&T coverage. Boom Mobile offers smaller plans cheaper than Verizon for Verizon data only plans, but device and setup investment will be $50 or more. Similar could be done with T-Mobile as referenced, but there's still the outlay for dedicated hotspot equipment given nobody really wants to activate data only plans on phones.
Alternately, you could get to know your neighbors and ask them nicely, though that's rapidly tapdancing toward a possible terms of service breach on their part and takes some real trust between people.
Personally, if T-Mobile coverage is an option, I'd personally may or may not just port my mobile number over to US Mobile and pick up a cheap Lumia if I were in your shoes as the prices are available and right for lighter usage. I use the Lumia 435 myself these days as my daily phone (and have been for nearly a year), it's a solid phone, easy on mobile data itself, and easy to tether.
That's about as good a recommendation I can make with the info provided. More info, better detailed solution. That said, if you're not allergic to reading, my more recent
mobile data guide for RV enthusiasts might have a few good tips for you on reducing data usage with any laptops or desktops used on mobile data and give you a better idea of the sort of hoops you'd jump through for doing mobile data on the various networks.