Using a third party like this is very risky specially when you are using one that is known to have many bugs. They could end up creating an invalid address for you and any coins sent to that address would be lost.

It is best that you handle everything on your own. Generating an address from a public key is a pretty easy task too (it is a matter of computing a hash and doing a simple encoding).
You can also watch those addresses using the Electrum protocol (https://electrumx.readthedocs.io/en/latest/protocol.html). You can hire someone to code this all for you.