I agree not to worry, especially in a multilingual environment. I used Logic of English with my dd this last school year (7-8 y.o), and it worked to solidify grammar for a straight-forward box checking math kid (my dd.)

We did MCT grammar island book before that, and will do Town and Voyage levels next year through an online class. DD's learned quite a bit of grammar in her Latin studies.

I'd recommend the free videos. http://www.logicofenglish.com/video/training

HTH
Bean