I would not recommend informing IRCC now. During these 2 months window (your trip in May) you might get your application done, if not you should inform them just before your trip. Good luck.
Congratulations! Based on what I've observed last month, the period people got their invitation letter ranges from few days to couple of weeks after LPP. Hope you get yours very soon.
As far as I know, kids' applications are done once the main applicant's application done. So, as long as your application is progressing, it is all good.