Surgery of this nature is painful, and really can affect a person's emotional status (faced with mortality, sometimes made to feel that they are responsible for the condition of their heart, ect.) so your caring enough to bring some nice dishes is going to be a very positive act.
If at all possible stick with as natural food as you can get. Little or no preservatives or chemical additives. Try to avoid any animal fats, although the recommended chicken seems ok. If they like seafood or fish, you could incorporate that.
Of course you'll be alert to not using too much salt, or high carb foods that offer little nutritional value (like white pasta, rice, etc.).
Fruit can be nice, but it can also be high in sugar and that is not recommended for post op recovery in many cases. Bananas are a good choice, better than the very high sugar watermelon or pineapple.
If they like avocado a Haas variety can add a silky texture to dishes without compromising the avoidance of "bad" fat.
Take care now and I hope your graciousness is appreciated!