Raising bilingual children is something like teaching your daughter to sew.

When you have an easy garment to sew, you might let her do the job. You may also be less fussy on a part that does not show. However, when you work on something that is more difficult or important, or something that shows, you might tell her to let you take over.

As a result, the clothing would come out fine, but your daughter's sewing skills would be stymied.

The same thing would happen with a child’s speech. If you discuss all of the easy or less important things in your native tongue, while saving the important things for the local language, then the child will quickly understand which things are important. You will indeed get your point across on those important things, but the child’s language skills in the mother tongue will be compromised. Yes, you were able to get your point across, and at the time that was the important issue, but your technique is educationally unsound. It is defeating in the long run.

Let bilingualism come naturally to your child. Let them experience all the aspects of translation, without worry about destroying the garment. Let it become a natural element in their lives.

After all, that's the way that you learned how to talk.