Do I need to heat the whole space like we have with our current heating system?

No, you don’t, infrared heating in large commercial spaces targets objects and people directly, rather than heating the air volume. This allows for zoned or spot heating of areas where only occupied or high-use areas are warmed. This greatly improves energy efficiency as you are not heating the whole volume of the space but are focussing on heating and controlling the comfort levels for people below where heaters are mounted.