Also following with interest as despite being almost 50, I have still not got the hang of meal planning 
To be fair, I found it easy enough when it was just me to cook for - but now I have:
Me - vegetarian
DP - who moans if he's given a meal without meat
DTS1 - incredibly fussy beige eater
DTS2 - thankfully a very good eater but stodgy foods only - cottage pie, sausage, mac & cheese etc
It's the combination of all of these which makes me give up at the first hurdle 
I did find the Eat Your Books website useful, when I subscribed to that - just didn't get quite enough usage to justify the subscription fee. I'll definitely take a look at the other apps mentioned here - the Batch Lady and Bored of Lunch cookbooks are great too and often on 99p Kindle deals.
@calishire that meal prep book looks very helpful! I also like the Sarah Rossi books for meal planning, she has lots of free recipes on the Taming Twins website as well.
@EveryKneeShallBow I am in awe of your neat recipe keeping!!
If anyone has a website/ app that also helps with using up leftovers, that's my current challenge... for example, I have tons of fruit (apples/ peaches/ apricots) which needs eating up, and I can't think of much to do with it apart from fruit compotes and maybe crumbles...