If you're feeling lucky go with 6 mortars and two steam tanks. If the Lightening Bolt comes up once early in the 3rd game you can say good buy to most of your mortars, and your steam tanks will be all but worthless at that point if they take more than 1 or 2 wounds from it. I'd definitely do a Knights of the Dinner Table purging on your dice, then some luck rubs on them. Then hope your opponent is ok with you rolling all the important stuff, like LOS rolls in scenario #1 and random event rolls in scenario #3. If you are lucky you'll keep rolling a Tsunami in #3, which should go a long way towards ensuring a victory for you in that one. Just remember to move a character out to control the objective as someone has to control it in order for either player to win.
I'm still debating on exactly what I want to take. I know what I'd really like to take, but in light of the scenarios I'm changing it some. I think it's silly to not take any war machines, but I'm not going to take as many as I would normally do in a 3,000 point game. I'm really going to have to assemble a bunch of minis before the tournament though, as what I have assembled is for my normal games, not the 'Ard Boys tournaments.