does 24-word recovery seed recover just bitcoins or all coins? I keep Bitcoins, Bitcoin Cash, Bitcoin Gold, Ethereum (via My Ethereum Wallet) and Litecoins on a Trezor.  

Question 1:  In the event that my Trezor is lost or destroyed, will my 24 word recovery seed restore my access to just the Bitcoins, or will it recover the other coins as well?

Question 2: If the answer to Question 1 is "just the Bitcoins", then what should I be doing to preserve my access to the other coins in the event of a lost Trezor?   Is there some way to  display my private keys and copy them down on paper? Or something else I should do?
Yes, you will have access to all of your cryptocurrencies.
The 24 words seed is used to derive the master key. Keys for all cryptocurrencies are derived using BIP32 and BIP44.
You can check out the BIP44 Mapping Table.  

The 24 words seed can be used on BIP39 compliant wallet like Electrum.
The private keys can also be accessed with BIP39 Tool GitHub or the online version (I don't recommend using it online.)