"Romantic Road" Japan, including rental car and trains

we're hoping to drive the Japan "Romantic Road" to Nikko in late Feb/early March 2015, starting and finishing by train. E.g.

Tokyo to Sakudaira via Shinkansen
One-way rental car from Sakudaira
numerous "onsen" along "Romantic Road"
Train from Nikko back to Tokyo.

We are mom, dad and a baby. I can read rudimentary Japanese (i.e. sounding out words in kana). I have plenty of international driving experience so adapt to observed conventions pretty quickly. I have a valid IDP. We would likely take our own baby carseat which attaches via seatbelts.

Question is simple: Is there anything really stupid about this plan? or any suggestions specific to this route? As far as mountain weather this year; or the cost effectiveness of one-way car renting; scheduled local festivals along my route around 1-5 March; or rail-car-rental bundles I should know about?

Note: I have seen http://www.ekiren.co.jp/phpapp/syouhin/index.phtml?syouhin_cd=008 but I can't perfectly understand the requirements or even how to order. I have inquired for the order form and will see if I can understand/translate that more fully.

Best Answer

Your plan sounds otherwise OK, but you're going pretty early in the year: it's still going to be cold and wintery in Feb/March, with lows below freezing and occasional snow. I suspect the scenery would be better later in spring or in autumn. However, the roads should be open, so this isn't a blocker.

Your IDP will be fine. For Japanese car rental agencies including a variety of English "wrappers" around Ekiren, see this answer. English road signage is pretty much universal in Japan, but cities can be tough to navigate (in any language!), so try to ensure that your rental car's navigator has an English mode. Also double-check that your child seat will be compatible, Japanese cars do not generally have ISOFIX points.