Have a look at
http://www.hotel-la-rochelle.com/ang/index.html The hotel is in the best spot in town, however, no aircon. and as being on the square is a bit noisy.
http://larochelle-tourisme.com/en/index.htm will help you with what to see and where to go.
Recommended restaurants are:
1. Les Flots positioned on the square tel: 05-46-41-32-51
2. Andre - On the square, sorry, no tel. on hand
3. Aunis - positioned in 14 Rue St Jean Due Perot (just behind the square), no tel. on hand.
All three places provide very good meal with Les Flots and Aunis being the better of the three and Les Flots the most expansive but elegant.
Don't forget to have your PNR and a/c documents.