Ok, I live just south of Ottawa and work in the city and would be glad to offer any assistance on local events etc.
You may run into some shortage of places to camp, depending on the month. I do know of a place around 40-45 minutes south that takes full season campers but will take short term campers upon notice and has full hook up, if they have empty sites.
I also would not cross the US/Canada border west of Toronto to head east.
If you do, Toronto is to be avoided at rush hour at all costs! The 401 is supposedly the busiest highway in North America (at least according to one TV show?).Every second vehicle is a transport truck going between Montreal and Toronto. When I'm driving on it I set my cruise at 95 kph (58 mph?) and let the traffic pass me - much more relaxing than trying to pass every few minutes.
FYI transports trucks in Ontario are supposed to be governed at 105 kph max so when one passes another it is referred to as an "elephant race" and slows down the left lane.
I would continue east in the US and cross at Ogdensburg NY (very nice dirve) and drive straight up the 416 to Ottawa (four lane divided and not too much traffic). The other route is to cross at the 1000 Islands crossing, then you only have around 40 miles on the 401 and then take the 416 into Ottawa.
Good Sam and Coach Net both work up here though you may want extra medical insurance (I have the same issue when I go to the US).
Cell phone rates here are some of the highest in the world! Check with your provider and ensure you have lots of minutes and data.
As for customs, tell the truth and no firearms. Also if you have a criminal conviction you may need extra paperwork. (A DUI conviction may make you ineligible - same as me going to the US).
Custom officers seem to be the same both sides of the border, there is the occasional one that has a bad day and takes it out on travelers because they can. The vast majority are very professional and courteous.
Expect higher prices, but the offset is that your dollar is worth around 30% more up here right now. Fuel prices along the 401 "enRoutes"are much higher than a few miles off the main highway.
Most "enRoute" rest stops along the 401 have diesel, but it may be hard to get into the island. You might want to park in the RV/Truck section and walk over and check out the fuel islands. All "enRoutes" have a restaurant and RV/Truck parking.
HTH
Chris