Best way to use LED Cinema Display & Thunderbolt Display with Macbook Pro 2016
Thunderbolt is a multiplexing of several signals - PCIe bus, USB 3.1, power and DisplayPort.  On the 2017 MBP you have at least 2 Thunderbolt 3 ports.  This means you don't need to convert from TB to DP/mDP as the signal is already there.

The LED Cinema display uses an mDP interface and the Thunderbolt display requires a Thunderbolt connection.

So, all you need is a USB-C (Thunderbolt) to DisplayPort cable for the LED display, and a Thunderbolt 3 to 2 adapter you mentioned along with the Thunderbolt cable you already own (from the previous setup) for the Thunderbolt monitor.