Event Card mechanic needed

Hi everybody. Sorry I haven't been very active here the past year... I've been designing mostly variants to existing games as opposed to original things. But I'm working on a multiplayer version of my d6 Shooters game (http://www.boardgamegeek.com/boardgame/54201/the-d6-shooters), and I'm looking for some help and input on one aspect of that (well, one aspect for now!).

The original version is a solo game where you move your posse along a map. Every so often, one of the spaces on the map triggers an event, and then you draw an Event card and resolve it (or roll dice and consult a table if you don't have the cards). I like the events being there and the flavor they add, but I was never crazy about them being at fixed locations on the map. It always seemed wonky to me that events would happen at the same places, but it was more that I was trying to convey the idea that events would happen every so often, or that certain places were more likely to trigger them. Anyway, I'm okay with that being the case for the solo version, but for the multiplayer (2-4 player) game I wanted to change that and make it more of an interactive thing.

Here's the idea I've been playing with...

There is an Event Deck, and each Event Card has both a good event (e.g. Gain 1 Food) and a bad event (e.g. Lose 1 Food). You get Event Cards only by rolling and locking a certain sequence with the dice (1-2-3-4-5), so they will only happen every so often, and players can choose to specifically "go for" an Event Card if they want. You hold Event Cards in your hand, and can play them at any time, either on yourself for the good ones, or on an opponent for the bad ones.

In a basic sense, I like that... It's simple enough and brings the events into the game. But my question/problem is that I'd want to encourage the interaction of that, and I'm not sure why a player wouldn't just always opt for the positive side of that. Or, at least, certain players might always opt for the positive side of that, and others the negative. You know what I mean... some people particularly relish playing "take that" cards on other players, and some people would never want to do that. So the goal is to make it more of a difficult choice, to encourage the passive players to use them as "take that" cards once in a while, at least, and to discourage the aggressive players from always using them as "take that" cards. Granted, certain situations in the game might make one choice or the other more preferable... if you already have plenty of Food then you're more likely to want to knock some Food away from the guy who's ahead of you... but my feeling is that by and large people might tend to use them in only one way or the other. Maybe I'm wrong, but in any case, my premise here is based on that assumption...

I was thinking that perhaps all Event Cards could be worth points at the end of the game, if they've been played, so whenever an Event is played on a player (either by them or by someone else), that player takes the Event Card and keeps it until the scoring. That would discourage the "take that" type of player from always using those cards for their negative effect, but then again, it would give extra reason for the non-aggressive player to never use those cards negatively... unless perhaps they also got some kind of "event token" to keep whenever they played an Event Card against someone else, and the tokens were worth some points, too. The idea being that it's not just the main objective of the game (traveling across state to confront a group of outlaws) that is important, but also the stories and fame that those who return will be able to tell. And sometimes you may get as much notoriety for stories that you tell about what happened to other people than for stories about what happened to you. And maybe it's not as cut and dry as each card being worth points, but whoever ends up with the most Event Cards getting a certain number of points... kind of like the "longest road" in Settlers.

Another thought is that if I skew each of the Event Cards between the two events, then that could help. So for example, instead of the two events comprising +1 Food OR -1 Food, it would be more like +1 Food OR -2 Food, or +2 Food OR -1 Food. That might make the choice a little more difficult, as far as which way you would want to play it. Or, it might make the choice more obvious, depending on the situation...

Another thought is to just have one event on each card, so it would have to be played either for you or against someone else. But I like the choice aspect of having two events... it's just a question about how to make that work effectively.

Any thoughts/comments/ideas?