First off, Welcome!!!
I haven't done either of the two kits you have mentioned, but I have built several guitars and can say that 20 hours isn't going to be anywhere near enough time. The typical time it takes to build a serviced kit guitar is around 100 hours and that is if things go well. If any problems come up, it isn't out of the question to add another 20 - 30 hours on to that.
I say if you have a place where you can continue your project after the class has ended then go for it. Honestly though if you are looking for a project that you can start and finish within that 20 hour limit, none of these kits are going to work. Heck, the big factory bulders like Martin take more than 20 hours to build a guitar and they have 200 years experience and lots of specialized tooling to get it done!
You might want to check out Grizzly
for their kits. The different kits they have are partly assembled and can be done in the 20 hour timeframe. My first kit was a Grizzly electric guitar and it probably took me 15 hours to do including the finish. They have a mando and uke kit that just might fit the bill for what you want. Just go here
and they have a listing of their kits.
Good luck and let us know how things go!