Angeloooooo ..... Bring a BIG umbrella, bug spray, and chap-stick .....
Seriously, you need to be somewhat concerned about a couple of things .... Be careful with the power supply, make sure it's adequate and protected from the elements, including the public ... I've done some outdoor gigs, and the wind is a factor for speaker placement because it can literally blow the sound right back at you, ... it will also be a factor if it is hitting the mic head on ... I might think even moreso with that classy 'retro' mic you have ... is there a 'wind screen' for that? .... Do a sound check as close to start time as possible ... and obviously if you are reading music ( which I don't think you need to do), the wind can raise havoc with that...
As for bugs, if there is one of those 'Mosquito Monsters' or what ever they might be called, DON'T set up next to it ... I did once, and while they kill mosquitos, it has to attract them first, and they may get you as they are taking that last trip to the chamber.... And there is always the possibility of sucking some in while you are singing ... NOT PLEASANT!!! ... and yes, the lips can get chapped and dry working outdoors ...
If I think of anything else I will let you know ....
Hope to see you next week ....
t.