Hello Andrés, ¨de paso¨ doesn´t have an exact translation in English, but it loosely means ¨on the way¨, ¨at the same time¨, ¨to end up¨, or ¨incidentally¨
To use your examples:
Podemos salir a dar una vuelta y de paso comer algo
We can go for a walk and stop to eat something on the way
Usted puede ayudarle y de paso conversar con él
You can help him and end up conversing with him
Usted puede divertirse y de paso aprender
You can have fun and learn along the way (as well)
Juguemos y de paso aprendemos algo
Let´s play and learn something on the way / at the same time