Glad your trip worked out. My father took us camping a bunch growing up, and it seemed like a camping trip we had planned was a pretty good indicator of rain that week.
But we survived, and still enjoyed the whole thing. Some good tips are in this thread.
When its warm, I usually wear crocs or similar on my feet, since your boots will get wet anyway and stay soaked for days. So I just wear my (fake) crocs and save the boots for hiking.
Good idea on the charger or power for phones and devices, these days most kids and even adults can't pass a day without their smartphone.
If you are car camping and you know it will rain, there are plenty of canopy set ups you can buy to save the weekend. But as long as it is just a rain a not a severe wind condition, $40 at home depot or walmart will get you a blue tarp, some cord, and a few spikes or tent stakes. Then you can set up a simple tarp canopy to keep an area dry. Here in the northeast, you can hardly find a camping spot without trees everywhere. So, in a pinch, you set your ridge line tight between two trees, and throw your tarp over it. Tie back the corners and midpoints to the ground or to other trees. This will work fine unless it is really windy. Then, you might have to hunker down more.
But you could still set up a basic, utilitarian shelter for a modest outlay that will help save the weekend. It is not that difficult, and field guys should know how to rig such a shelter. The hardest part is probably reaching high enough on a tree to set your ridgeline a good 8 or 9 feet up for headroom, knowing how to tie a line to keep it taut. If you had no other gear and needed a post, buy two 2x4's for $6, notch the top, and use them for your posts.
Years ago in the army during field exercises, we became experts in throwing up a poncho shelter in just a few minutes that would keep you (reasonably) dry. I always rucked a spare poncho with bungies on the corners, and some 550 cord, and could have a low poncho shelter set up in 2 minutes, tying off to the nearest small trees. You would want something far more spacious for a weekend trip, but the principle is the same.