The normal frequency range of headphones is about 20Hz/20,000Hz. These are perfectly suitable for use with your InnaPeace tracks and you will gain all the benefits advertised with a set of headphones with these ranges.
Here is a little extra information:
The human ear can detect sounds and recognize them as audible tones as low as 20Hz and as high as 20,000Hz.
You hear InnaPeace entrainment waves as pulsations rather than as actual tones with recognizable pitch precisely because for the most part they fall below the 20Hz human hearing threshold. i.e. Schumann tracks are 7.83Hz.
Isochronic tones are not musical tones at all, they are pulses of volume going on and off and therefore have nothing to do with pitch.
Similarly, binaural beats are not created by the headphones, they are interference pattern between two carrier frequencies (both of which ARE high enough for standard headphones to reproduce them) created by the brain "inside" a person's head, hence they are not affected by frequency response of headphones.
Monaural tones are also created as as an interference pattern unaffected by headphone frequency response, but are created individually inside each ear rather than just one time between both ears.
These are the 3 types of entrainment technology utilized within your InnaPeace tracks so using a set of headphones which fall within the 20Hz/20,000Hz range will work perfectly fine.