Well, there are a couple of ways to look at this. You are letting your pups train you into being fussy by catering to them. THey will NOT starve if you put down their food, pick up whatever hasn't been eaten and make them wait for the next meal. They may miss a few meals, but they WILL eventually cave, and start to eat what is put in front of them. That's the story from a training perspective.
HOWEVER, would you be happy eating freeze dried back packing food at every meal? It might meet your nutritional needs (barely) but it would be pretty boring. Is it a surprise that they are happier when you spice it up a little for them?
Just make sure that whatever you mix into their kibble is good quality, lean protein, without a lot of salt or spices. I would stay away from canned tuna, because it contains a lot of heavy metals. They are suggesting that humans limit the amount of canned tuna they eat, and our dogs are SO much smaller!!! But pieces of lean meat from your own dinner is FINE, as are eggs. And you don't have to limit the eggs to once a week. A half and egg, scrambled, and added to their food once a day is fine. In fact, this will really improve the nutrition of your kibble diet, because most kibbles are lower in protein than is ideal for a healthy dog anyway.
DO consider Honest Kitchen, though. It's a great alternative to home cooking if you want something easier, and is SO much better nutritionally than kibble.
I'll post a new thread showing how I make Kodi's food using HK. I make it once every 3 weeks or so, and (other than freezing time) it takes me less than an hour. I'd spend more time going to the pet store for another bag of kibble!