Reddit reviews Park Tool CT-5 Mini Bicycle Chain Tool

If you don't have one already, you'll need a chain rivet tool to remove/reinstall the chains. Here is an inexpensive example from Amazon. You can get even cheaper ones at Walmart, if I remember correctly. Park Tool is a pretty solid brand, though and name-brand chain tools can certainly get much more expensive.

And a video on how to use it.

I've used Kmart/Walmart chains on 10-speed bikes before and they've worked OK. I wouldn't put one on my fancy road bike, but that's another story. You can also order higher-quality, but still cheap, chains online. Example.

I second the WD-40 soaking. If the chains are greasy, gasoline works as a cheap solvent (just be careful!). Most chains that just have surface rust can be rescued.

Best luck on the project bikes, I'm sure the kids will be thrilled!

You may need shorter chainring bolts like these (first link I found - you can get cheaper ones) or some chainring bolt spacers. You'll also need to adjust the length of your chain with this but you can also borrow one from your lbs. It would not be a bad idea to get a new chain at the same time, but if you're on a budget don't sweat it.

I'm going to have to replace my chain soon. My bike has the KMC Z410. Should I just stick with that?

And I'm going to have to get a chain tool. What's the difference between these two besides the size?

https://www.amazon.com/gp/product/B000OYHCHG/ref=ask_ql_qh_dp_hza

https://www.amazon.com/Park-Tool-CT-3-2-Chain/dp/B009ZN1Q0Q/ref=pd_sbs_468_2?_encoding=UTF8&pd_rd_i=B009ZN1Q0Q&pd_rd_r=QMERK200R8D5N2A998P9&pd_rd_w=KR1Ih&pd_rd_wg=Dc7ou&psc=1&refRID=QMERK200R8D5N2A998P9

Since it's going to be my first time, should I just take it to a shop?

Park.