Seriously Lazy, if your kids are snacking because they are bored, then having "juicy" lunches won't help. You need to address the boredom. Your kids are bored because they have nothing to do and no routine. They should be following some form of homeschooling timetable. I get that some parents don't want to do the conventional "sit down and study" method of schooling but you need to at least give them learning activities! She should be setting them tasks to do throughout the day, not just leaving them to their own devices. Both Isla and Esme should be getting some 1to1 schooling from a parent for at least part of the day. Isabelle is old enough to study herself but she needs to have objectives and outcomes to meet, not just copying endlessly from Wikipedia.
Also if you're going to try and cook new things, involve the girls. Get them prepping the ingredients, reading the recipe and learning how to cook. They all should be helping with things like that.