If Château Frontenac offers such a deal for military personnel, I would definitively go for it. Great location; very easy to do everythings by foot.
Since you are in the area, I hope you will go a bit further east, in Charlevoix. Nice views of the St-Lawrence. And if you want, you can take the ferry at St-Siméon to cross the river (the crossing takes about 65 minutes) to Rivière-du-Loup or at les Escoumins (90 minutes to cross the river) to Trois-Pistols.
Also, if there is such a deal for Château Frontenac, check if Fairmount offers the same thing at Manoir Richelieu, in les Éboulements.