I went hiking a week ago along Curley Lake Rd, in SW Gatineau Park. The mosquitos and deer flies were bad. I suggest you get them mosquito head nets, or nylon bug suits, if you have to walk in any distance where there is not a good wind. If they handle mosquitos well, you could get them Deerfly patches, that are disposable attracting flypaper that attaches to the top of your hats. If you go 1st down a trail, you'll get the most bugs.
An in-town hike / bicycle ride with wind to blow the bugs away, and exploration potential can begin at the bottom of the remains of the old mill off the bicycle trail in Aylmer, (opposite the City of Ottawa water filtration plant. and Mud lake). Because of swift current by shore as you proceed up river exploring, make sure the kids have their life jackets on. After exploration has finished, then proceed west to the Alymer beach and boat club at the west end of Alymer Rd (Rue Principale ?). There you'll find boats of all sorts, kite boarders, and a beach.