Concerns about moving luggage around

Hi, I am preparing for my first trip to Tokyo. It has dawned on me that I may face some considerable problems with moving the luggage around. Would appreciate if someone can help advise:

My itinerary is as follows:
1) Day 1 to Day 6 -- Stay at Prince Sakura hotel in Shinagawa.
2) Day 7 -- Morning train to Shinjuku and then to Hakone (08:53 train). Stay one night in Hakone.
3) Day 8 -- Afternoon train (15:18) from Hakone to Shinjuku. Then, transfer to Tokyo then to Maihama Station to Hotel Sunroute Plaza near Disneyland.
4) Day 9 to 11 -- Stay in Sunroute Plaza Hotel.

I am travelling with my wife and 2 kids, so will be carrying around 4 luggage, probably 2 big and 2 small ones. My worry is luggage handling from Shinagawa to Hakone, then, from Hakone to Maihama especially since we will be hitting the rush hours, especially in Shinjuku and Tokyo.

I suppose there might be a few solutions other than just lugging the luggage around:
a) Store the luggage in Shinagawa for one night and retrieve it upon return from Hakone before going to Maihama. But I am not sure if hotels would be willing to accept luggage deposits like that over night.
b) Store the luggage in Shinjuku Station using the coin operated lockers. But I fear may not have enough big lockers.
c) Use the luggage transport service to transport the luggage from Shinagawa to Sunroute Hotel. But I a bit worry about this cos not familiar with system and don't know Japanese language.

Sorry for the long question. Can someone advise me?

Thanks a lot. Appreciate it very much.

I would go for c). The hotel staff will be able to help you. Just have the address of the Sunroute Hotel ready. The address can be in English.

But b) sounds not bad either. It would be a little bit cheaper than c). But there comes the possible stress of finding vacant large lockers.

I wouldnt get on the local trains to shinjuku with luggage at rush hours. I've done likewise (4 cases, 2 kids) and it was a nightmare. With 3 cases you can usually fit everything in a taxi (sometimes I stuck one big one in the passenger seat, then squeezed 4 of us in the back), now that my kids are older and have a medium sized case each, we live with two taxis, they are not so exey if you arent going far.

I have experienced the no available large locker problem. This will severely restrict your mobility. Sightseeing will be a drag. There are more small lockers than large. If you want to use lockers, you need to get smaller luggage (carry on size) to be safe.

Luggage transport service is your best option. The concierge at your hotel will be able to arrange transportation of your luggage. Here are some links

http://www.japan-guide.com/e/e2278.html

http://www.planettokyo.com/news/index.cfm/fuseaction/story/ID/83/

http://www.accessjapan.co.uk/newlookfactfile/shinkansen1.html

http://www.narita-airport.jp/en/guide/service/list/svc_05.html

Thank you guys for your comments. They are really useful.

Yeah, option B is out.
Option A Shinagawa hotel confirmed possible to deposit luggage.
Now, exploring Option C.

This site is just awesome !!! Wished I had done my research here first before planning my trip.

Thanks once again.