Good timing on this question. It seems that a number of people may be arriving earlier than Wednesday (either because flight schedules make it difficult to arrive early enough on Wednesday to make it to Trois-Rivières by cocktail hour, or because they just want to visit Montréal.) Of course everyone is free to make their own plans, but it might at the very least be convenient for arranging pickup and transportation to T-R that such people choose a hotel or hotels in reasonable proximity.
After doing a (very) little bit of research, my suggestion would be to stay downtown, somewhere in the vicinity of Shaunessy Village, which is within walking distance (or a short metro trip) to most of the touristy things do see or do: Mont Parc-Royal, the Latin Quarter, St-Joseph Oratoire, Rue St. Catherine, Museum of Fine Arts, etc.
As far as getting there from the airport, there is a shuttle (
STM 747 ) that runs 7x24, 2-5 times an hour during most of the day, that drops off at various downtown locations. (Costs about $10 and takes about 25-40 minutes depending on traffic and stops.)
We might be able to arrange a discount at the Montréal Delta, although it is considerably more expensive (about $246) than the one in T.R. A quick look on the booking sites suggests that there are several reasonable choices to choose from.
I suggest that people who are interested take a few days to think about it, look into it, comment, etc. and then perhaps next week there will be enough information to make an informed choice.