Our humble opinions, based on more that 20 trips into Canada form the Pacific Northwest mostly by boat, but some by land to snow ski at whistler.
1. Canada, specifically British Columbia: A wonderful place to visit and see. Great destinations and something for everyone. Awesome mountains, parks, cities. Generally safe and clean. GREAT people and hospitality. We've returned almost every year because we like it.
2. Border Crossing (both directions): Have a passport or other proof of citizenship for every one. Some states like WA offer enhanced DLs that work, but we carry our passports anyway. Bringing pets (like we do)? Bring evidence of rabies vaccination. Don't carry more alcohol, tobacco, or other items than is allowed (easy to find the limits on government websites). Don't carry prohibited foods and other items. Leave guns and ammo and home like we do UNLESS you make proper arrangements for long guns in hunting situations. NEVER lie to border crossing officials unless you enjoy long, difficult conversation's. We've been boarded (on our 47' 1952 Chris Craft) at the customs dock several times in both directions (and once on open water by US Homeland Security) and been thoroughly searched (the boat and us). The same is possible in your RV. Border crossing officials are almost always polite and pleasant - unless you give them a reason not to be. We've always been honest (even when carrying somewhat more that the amount of alcohol allowed into Canada) and never had an issue. A friend was boarded a few years ago with over 60 bottles of undeclared wine, and he paid import duty and a fine to get off the customs dock. And had a long uncomfortable discussion.
3. I'm a past BATFE Licensed explosive possessor and blaster (and thus easily found in Homeland Security imagery and passport databases used by US Customs) so US customs officials usually smile and let us go with minimal interaction. Even so, I would NEVER try to conceal anything during a border crossing.
Have fun in Canada!