Advice for an Across-the-USA RV Trip?

We're planning a family trip across the US by RV in March, from San
Francisco to Cleveland. It's not the kind of thing I've done before (well,
not since I was 10), so I'd appreciate any advice anyone might be able to
offer.

In particular, I'd want to have phone and internet access while on the
road. All the phones we have here in Japan are simlocked , so I'd have to
probably buy a couple of cheap phones, and perhaps rent a mobile hotspot? Suggestions
appreciated...