I think it depends on the time, place, and crowd.
I think I would leave the date off the favors - I prefer most things undated - but that's just me
Maybe you could have them on the lunch table and each guest could pick it up then?
Or hand them out during the first game? (If you play games at the shower)
If they are different colors, the guests could play "the dice game" to select one - at the end, if anyone has more than one, she can keep the one she likes best, and put the rest "back in the pot" for the ones that didn't get one.