Using cards for actions = too unpredictable?

A couple games come to mind, not all of them flattering.

• Candyland. Simply draw and respond. This is likely the most elementary replacement of dice with cards.
• Screaming Eagles. Each turn, players have a host of cards to choose from, detailing a direction and a speed. They choose the one they want, and then play it face-down. Cards are revealed in order, and the action you chose might put you in a good or bad position, depending on turn order. I think of this as an introduction to "programmed actions."
• Robo Rally. Pretty much the standard in programmed movement - although this game is fairly old. From a hand of cards, choose which actions and the order you want to execute those actions, placing them face-down in the play area. When you reveal the cards, the actions are executed: moving, turning, firing weapons, etc.

From the sound of it, I suspect you want to have something like what appears in Screaming Eagles. I'd suggest wob's multiple-card assortment as the foundation. Allow players to draw three, pick one to play, and discard the other two. This allows for the randomness and unpredictability of dice results, with the added ability to mitigate "bad rolls" and/or to optimize one's choice from a smaller host of options.

Space alert does this. Cards are divided into two sections. Players play a card and do the action in the upper half of the card (the card can be oriented either way). The available actions are move or to do the "A" action or "B" action in the room that you are in.

That seems like it could be a possible direction. I was thinking that there should be a way to use the cards in a sub optimal manner. (It would be useful for a situation like if a player had all heal cards, but everyone is at full health) My take on it was you could have a typical card provide like 2-3 movement points or healing or whatever, but have the ability for cards to be played face down for one movement point, healing or whatever.

Good luck with your game.

There are plenty of games that does that. One game in my collection that comes to my mind is "Age of Mythology". If feels like Puerto Rico, but each player have a set of 7 basic action cards. But there is also a deck of random cards which are more powerful version of the 7 basic action.

At the beginning of their turn, the players choses X action. First from the basic actions and the remaining cards randomly from the deck.

So you chose the basic actions you really needed to do, and you tried your luck with the deck of cards, for other actions you might want but more powerful.