One of main objectives of Cosmic Rays Extremely Distributed Observatory (CREDO) is the~search for Cosmic--Ray Ensembles (CRE) - occurrences of correlated Extensive Air Showers (EAS). In~order to~confirm the~existence of such phenomena large scale measurements of EAS signals and an~analysis of their correlations in~time are necessary. To~make such observations possible, infrastructure of low-cost detector devices spread over the~Earth and connected in~a~global network should be developed. The~individual detector system registering an~EAS should at least be able to~give information about the~time of detection. Such basic measurement can be performed by a~few small scintillator detectors connected in~a~coincidence circuit. This study focuses on~measurement using an~array of very small detectors (area of $5\ cm \times 5\ cm$ each), which is currently being assembled. To~determine if coincidence signals in~such type of array can be a~sign of an~EAS event, a~simulation-based analysis was conducted. Results from it are consistent with expectation that coincidence events caused by air showers have frequency orders of magnitude higher than those caused by all background sources, including uncorrelated single particles originating from low energy Cosmic Rays (CR). The~analysis is based on~multi-dimensional analytical parameterization of cosmic--ray showers derived from CORSIKA simulation results. Using such analysis it is possible to~test expected efficiency of various detector systems and consider different models of cosmic ray spectrum composition without repeating time-consuming simulations. Presented work includes details of detector setup, simulation based predictions and planned measurements.