Oh thank you so much, Maegan! and, these are ALL great suggestions

i have printed the calendars a time or two

...and i swear i have done it differently every time - LOL!
so...i THINK what i'm going to do this year is use the TWO page calendar...have it printed at a lab (just to save myself the time and frustration)...and then mount each print to a piece of black cardstock. That way - each page is nicely framed and has a great weight...plus - i don't have to worry about printing double-sided, etc. Plus - that way the binding will be through the cardstock and not the calendar, kwim? BUT - i will say that i HAVE done the double-sided printing and it is super simple.
i have also used everything from glossy to heavyweight matte paper and honestly like all of them - LOL! when you use glossy paper - you can still write on it with a fine tipped sharpie marker and of course, the prints turn out awesome! with lustre...you can use a sharpie or a nice pen. and with matte - everything works (my fave option)!
definitely check with your local kinko's or copy shop...they CAN do the printing and the binding...and in the end - it might work out to be more cost effective when you take into account your time, paper, ink, etc.
i also plan to have a couple of the TWO page calendars printed and bound to use as a desktop planner (not going to mount those on cardstock as i don't want them to get too big - lol)!
there really are SOOOOOO many options...but most of all - i just hope you have FUN with them...and if you gift them...that everyone who receives them LOVES all of the time and thought you put into them...who wouldn't?