to make translating easier.
A foreign language should never be taught through the translation method because languages don't translate word for word. There isn't a textbook on the planet that will enable you to do that! So give up on that idea immediately.
explaining the nuances
You shouldn't be trying to at this stage.
matching games
That's a much better approach.
Bear in mind that when a child goes to school in a foreign country where they don't know the language at all, they don't learn by having everything translated into their native language, or by having the finer points of grammar and syntax explained to them. They learn by listening and drawing conclusions about what is being said from the context. (Receptive language)Then they gradually begin to produce those phrases themselves (expressive language). Just using basic Polish with your children every day will make a big difference but it takes about six months to see results.