"Panel has a built-in charger protection"
It has protection against discharging the battery backward through the panel at night.
It does not have over charge protection. That's OK, because over charging is not going to be much of a problem with a 6W panel.
"a switch to flip the current from the batteries to from the panel"
Do NOT do that. A panel with no battery will have power spikes, and dips. It will kill the electronics. Quick.
The battery is like a shock absorber, keeping the electricity in a stable condition.
Easiest way to think about it is like 2 systems. One charges the battery, the other powers stuff.
The panel connects to the battery.
The outlets and lights connect to the battery.
It would be a great idea to have a main 10 amp fuse very near the battery Pos, and maybe another very close to the battery Neg. Just in case.
The battery must be in a good solid case, where kids can't set a conductor on the battery, like a wrench, knife, pipe... Kids will be kids.
Wire could be 14-2 w/g UF-B. ("Grey romex" at the store where the kid doesn't really know what he's looking at) Plastic top staples.
Terminal blocks are a good idea. Probably inside the battery box. Kids are kids.
Remember to re-tighten the screws in a day or 2. Ox-Gaurd (sp?) on the terminals and wire will help keep corrosion problems down.
Remind the kids to shut off the light. Games don't run from dead batteries.
Now the hard part. Telling you 6W isn't much power at all.
The light bulbs will need to be dim and low power, 10 watt? Only one would be best.
GameBoys, etc, don't use much power. Lights do.
There are some fluorescent lights available that have a jack for 12V power. AA battery operated, maybe at Lowe's / Home Depot. $8? Not great, but workable. Radio Shack store can make the power wire.
Paint the inside white.
Or maybe a clear round marker light with a 6W bulb from the auto parts store.
Batteries go dead from sitting. The 6W panel is just a little more than needed to keep up.
Two batteries need twice as much power to keep from going dead from sitting.
Best to use only one battery.
Check the battery fluid levels every so often.
Check the battery state of charge every week or 2. It may need grid charged sometimes if the panel is not keeping up. Using low batteries will ruin them in short order.
It could be worth the money to add a second panel later, depending on how the system works.
G-