There are many good quality commercial multi-port Power Adapters that have four power outlets of adequate output to fast-charge (where supported) your Apple iPad's and other devices. Extending to more than four charging ports will considerably restrict your options.
When selecting a multiport Power Adapter, ensure that it supports USB PD (Power Delivery). Apple does not support QC (Quick Charge) or other proprietary charging standards.
By example:
- mophie speedport 120 4-port GaN wall charger (120W)
https://store.apple.com/xc/product/HPZE2B/A
Two four-port Power Adapters would prove eight charging ports - and reduce the immediate impact if one might fail or be otherwise unavailable.