Charcoal is often used in potting mixes and fish filters to absorb impurities that can freak out living things. It's a good additive to have in a mix. Peat I'm less sure about. It does make for a wetter mix, and reduces air flow to the roots.

If it's all you can get, you'll need to add perlite or some other "spacer" to recreate air access to the roots, and you'll need to sort out your watering schedule to compensate for the longer moisture retention.

McJulie