I'm making a card game based on Triple Triad, which involves two players holding 5 cards that they place anywhere on a 3x3 grid. The cards have 4 values in the North, East, South and West positions and the objective is to hold the most cards by the time the grid is filled. The player can place a card next to an opponents and their opposing values will be compared, with the higher valued card 'taking' the other card.

My version of the game is 2D like the image above and I'm just wondering how to go about making the 3x3 grid and the cards as I don't know if they should be objects or whatever. The user should be able to select a card from their hand using the mouse and click anywhere in an open grid position and the card should then be placed there.
Does anyone have any tips on how to go about doing this sort of thing within NGUI?