I agree mostly with everything Framah said.
You might also want to think about what level of "archival" you are interested in. Printing on canvas and doing a gallery wrap with an acrylic coating isn't considered "archival" to many people, and certainly not if you expect the pieces to command a decent price. Or course, it depends on who you talk to, but personally, I think that a canvas gallery wrap is just a nicer version of a poster, not a fine art collectible piece.
Dibond is a great choice for archival purposes I believe. But throwing a laminate over it, is not. If you want these to be gallery or museum quality pieces, you want to minimize what permanent changes you make to the original print. Nothing garauntees that an acrylic coating or a lamination coating won't crack, peel, yellow, or have trace amounts of acid in it that will degrade the print long term. Along a similar line, to be truly archival, dry mounting is out too. My alternative idea to just hang the prints between bars is also obviously not archival and would be good only for temporary display. I would never do this for a gallery print.
As to the recommendation of the plexi-sandwich... you really really should never have a print touching a surface (glass, plexi, acrylic or otherwise). This is framing 101. That link provided above... it looks nice, sure, but it's really shabby way to preserve a print. Along with the print touching the glass, there is no edging to keep dust, smoke, and other contaminates from finding their way inbetween the sandwich. Part of what a frame does is psuedo seal off the print sandwich from the outside world as much as possible.
Just some things to think about. How serious do you want to take this?