Hi!
Foremost, I would like to wish you all the best for your preparation. It is an amazing journey.
Considering the fact that you want to be done with your preparation and appear for GMAT within a month, I suggest that you start with one of the free GMAT Prep CATs to ascertain your strengths and weaknesses. Spend sufficient time analyzing the answer choices. Make sure that you selected the correct answer choice and eliminated the wrong choices for the right reasons.
After you have determined your weak areas, work on them either by doing the
Manhattan GMAT Strategy Guides or the Veritas online course. I believe, doing both in less than a month may be suicidal. Remember, too many cooks spoil the broth. As regards study plan, you can check this out:
https://gmatclub.com/blog/2012/02/1-month-gmat-study-schedule/ You should do all the questions in the
OG and the GMAT prep. You may consider buying the additional question pack. Always, make sure to analyze your responses. There is not better prep than to gain experience in handling each question type and sub-type.
You can make use of Flashcards for on-the-go prep. You can even use them while you are attending nature's call. It may seem funny, but it really helps to prepare in these short periods.
Magoosh provide free mobile apps for math, idiom and vocabulary flashcards. You can download the GMAT Club toolkit app and access the flashcards. You can also print out the GMAT Club flashcards.
Apart from above, Veritas has a free app for on the go prep. You will be able to select the question type you want to practice and the number of questions. This app provide quite handy analysis of the answer choices. Since, you have Manhattan strategy guides, make sure you understand and use the navigator tool available at Students Centre of their website.
Lastly, I would suggest don't over-burden yourself with the prep. Keep sufficient time for yourself and your family.
Regards,
Nalin