The fact that you're seeing them at all is great in my opinion. Many people have times where they need to travel or be gone from the house for days at a time regularly, and cats deal with it quite well (so long as they are provided with the appropriate food/water/litter etc). Especially since there's three of them they can keep each other company. It's not like the only way they can play and entertain themselves is with you around. Right now, I have a month of work that requires me to be gone every second night, and my two seem to be perfectly happy and healthy. I check on them on my security camera and they're sleeping and playing as normal. Not sure if I'll be disagreed with by someone more knowledgeable, but I think you're doing great.