Here's a well-thought-out, specific guide to putting together a "ten essentials" daypack for hiking.
If you’re just getting into hiking, everyone is going to recommend that you pack the 10 Essentials when you go for a hike. Then they list about 30 pieces of gear that you should bring with you, but they never actually tell you WHAT to buy. If you find this frustrating or confusing, or worse, you’re going for hikes without the 10 Essentials, I’ve pulled together a few sample gear lists for different hike durations (up to 4 hours and more than 4 hours) that I hope you find helpful.
When you're hiking with kids, you might need a few extra essentials, but it isn't hard to extrapolate them from the listed "ten essentials." Have adult medications in your first-aid kit, like ibuprofen or antihistamines? Maybe you need the same stuff in liquid-dropper form for your little people. And if your kiddoes resist plain water when they're cranky, you might need some drink mix powder just in case you really need to coerce them to hydrate.
In general, put together your emergency pack based on things that are likely to happen. For example, I have already learned the hard way that if anyone in your party is hiking in newish footwear, it pays to dedicate some space in your first aid kit to blister care.