Problem caused by unconfirmed transaction chains
A few simple ideas get around the unconfirmed-tx-chain-limit you're running into:

Start with more UTXOs. Each UTXO can be used to create &lt;25 unconfirmed child transactions. So if you need to make n payments, you'll need at least n/25 UTXOs to do so using this method.

However, you can definitely do this in a more cost-effective manner. As Murch mentioned, batch payments describe the method of creating a single transaction with many outputs. So instead of paying one customer per transaction, you can pay many customers per transaction. 

Another option is to use the lightning network to send your payments. Lightning transactions are extremely cheap, and fast. If you are regularly sending small payments, I'd encourage you to consider this option.