Either or... and no you don't have a good plan unless this is a suicide mission... too many factors that could easily go wrong for you, and these are Pokemon... a lot of pokemon. even if you cut yourself off Pokemon fly (and can carry others), levitate, teleport, and there are enough of them that once you open fire from the building they can remove the entire building before you can react.
Its an army... a big one... Also your not going to be able to get them all with your traps there are too many of them.