You can try using Kiriging with semivariogram algorithm. In ArcMap (10, 10.1 or 10.2) select  the Geostatistical Analysit tool ---- Geostatistical wizard --- Kiriging ---  simple or any other algorithms --- then semivariogram.

I ever used saga-gis to analys peat depth. The result is almost the same with the real condition, althoug the position point sample is scattered randomly. To confince the result i used land cover condition, because LC has correlationwith peat depth.