Can an electron carry only one charge?
Yes, every electron is negatively charged with \$-1.602 \cdot 10^{−19}\$ C, meaning that for an electric charge of -1 C it is required to have \$ 6.24 \cdot 10^{18}\$ electrons. Sometimes the term "unit charge" or "elementary charge" (often denoted as \$e\$) is used to refer to the electric charge of an electron \$-1.602 \cdot 10^{−19}\$ C

Your concept of soldiers carrying charges and food (but remember to feed your soldiers before they go on a journey) seems to be correct. However, an analogy which probably is more widely used is water. Flow of water droplets adds up a bit like the flow of electrons in an electric circuit, and laws like Ohms law, Kirchoffs current law and Kirchoffs voltage law are all easily translated.

A short description with animations of the water analogy may be found here