If you are living in your RV full time then you should be just fine to leave it on all the time. Assuming you are using it on a regular basis. If you are new to maintaining water heaters you may want to read through this Water Heater Basics Article
Sounds like most of the bases are covered for you here. After 10 years we still struggle with some of the winter maintenance issues. A neat article about RV winterizing if you want a overview of cold weather storage.
I would think kids would enjoy the Nexus 7 more. Certainly more versitile than the ipod. The only trouble is Apple seems to have the "cool" factor for kids. Tough choice. I would think the larger screen would make it useful for school activitis like ...
