Previously, you said you had: Canon T3i body, Canon EF 50mm 1.8, Canon EFS 55-250mm, Canon EFS 18-55mm and one Yongnuo YN560-II.
Where are you in Canada?
What do you want to sell and how much are you hoping to get for it?
Henry’s in Toronto takes in used gear, though I don’t know how much you would get for a rebel and kit lenses. You could check their web page. Look for their show page as well, it is in a couple of weekends from now, I don’t know if they have an opportunity to move old equipment but they have good, free, seminars.
The 50 mm 1.8 and flash should work with your new 5D. Unless cash is extremely tight, I would be inclined to keep what you have for those times you just want to carry something light while walking around.