Bro candy cane lane is not hard the only hard one is mission 5 castle seige considering only at wave 5 a boss with 3k hp comes with 500 hp bosses following it, 3 bosses including 28k grave digger, 30k. Korblox deathwalker and a 90k fallen king
you do get quite alot of money though, I just spam scouts, place 4 mortars, spam more scouts till tower limit and get all scouts to lvl 3, then when they give like 200k cash I sell scouts for engineer and then acccel