Caen city centre is very popular with tourists. You will easily be able to find a hotel in the centre, close to the conference site, accessible on foot or by tram. You will find below a list of hotels in the city referenced by the tourist office.
https://www.caenlamer-tourisme.fr/manger-dormir/dormir/hotels/
Or Hotels with negotiated rates
Hotel Astrid (from €79 per night, €10 breakfast + stay tax)
https://www.hotelastrid.fr/
Hotel Bernières (€60 per night, €8 breakfast + stay tax)
http://www.hotelbernieres.com/
hotelbernieres@wanadoo.fr
Hotel des Quatrans (per night, incl. breakfast : €81 single - €95 double + stay tax )
https://www.hotel-des-quatrans.com/fr/
contact@hotel-des-quatrans.com
Hotel la Fontaine (€98 per night stay tax included ; 12€ breakfast)
http://www.hotelfontaine-caen.com/
contact@hotelfontaine-caen.com
