You'll have to get a small little project box (if I recall also talked about in this thread) to tidy this up and of course the DC power to power it but ..."neither snow nor rain nor heat nor gloom of night keeps this little relay from controlling my DC lights way out beyond the reach of wire" .
You could even set it up where she could use the relay to turn them off/on while HE would automatically made sure they were turned off by time X (just not during the bewitching hour of the annual time changes as I just learned).
Of course, depending on age, those lights might be a nice middle-of-the-night security blanket... and you'd be better off investing in good rechargeable batteries and just leave em be. Until she's a teen, and then the ability to flash those lights, sound alarms, and turn on the sprinklers would all be nice features around that tent. 
