We used the vouchers last year. Wishes fire works veiwing is by the smoking area in front of the ?plaza resturant, down the steps by the water. there were trees in the way for my liking. I prefer to watch wishes from main street as i like to be in the centre of the castle, i did not like being off centre. Also we do not have children, so i can always see and do not mind the crowds.
As for the Illuminations of earth (EPCOT) the viewing lake is down some steps by Morroco, again i felt i was too far away and off centre. i prefer to watch Illuminations of Earth from the shop that stands by itself from the walk from Future world to world showcase. the shop is at the top of a slight gradiant, and we have never had a problem in finding a space. as well do not have the issue of children who cannot see over the top of adults heads.