I'd suggest that you do both, but to do both as a single day trip. Do a Fukuoka day trip from Hiroshima, and a Kanazawa Day trip from Kyoto. Hataka Station in Fukuoka is about one hour away from Hiroshima Station, and Kanazawa is about two hours away from Kyoto.
I would try to plan your travel in the early morning and evening, when places you want to visit are closed. When I looked up the trip on Hyperdia, taking the JR trains from Tokyo to Kanasawa would take 263 minutes, which is almost four and a half hours. I would suggest smaller hops. There are exceptions to this rule, like when you are trying to be somewhere in the evening, such as the yatai stands in Fukuoka, or the Gion district in Kyoto. Fireworks and Night Illuminations would also fall into this exception.
I would also recommend going to Miyajima as cloce to a full or new moon as possible. You will get the largest tidal shifts at the floating Tori gate. The Gate will be "floating" late in the morning (9:30-11AM), and "beached" in the afternoon (3:30-5PM). If you make Miyajima a full day trip near April 4th of 2015, you should get both views.
High tide +3.42 meters @ 9:37 AM
Low tide +0.42 meters @ 3:31 PM
If the only reason to go to Fukuoka is for the Ramen, your should be done at Miyajima around 4PM and could be back to Hiroshima Station aroud 5PM. You could board a Shinkansen for Fukuoka and the Yatai stalls for dinner.
As for fireworks and Illuminations, do you have any interest in these. The might be some fireworks in Atami (between Tokyo and Nagoya), and the winter Illuminations in Nagashima Park in Nagoya go through the end of March, so you might look into these.
Here is a link to Nagashima:
http://rivercam.wordpress.com/2010/04/01/jp%E3%80%82winter-illuminatio...I also remember something about a night flower viewing somewhere in Kyoto. I don't remember where.
I hope this helps...