We ALWAYS eat at Sci Fi each trip, as my nephew LOVES it. It is myself, my sister, and her son/my nephew, age 8, so there are three of us. He sits in the first row with one of us (usually me) and other other adult (usually my sister) gets to sit in the second row alone. I do say GETS as, like Pixiedust 34 just said, it's a nice break.
But with the movies playing constantly, it's not like my nephew and I chat much. Last time he even said, "can I just have some quiet time and watch the show?" He needed a break, too! There's not a lot of chatting going on in the entire place, actually, everyone is watching the show.
I will say when we've been a group of 5 (when the husbands went) we still never sat more than two to the row. But since the OP's children are 6,5 and 2, they shouldn't have a problem in one row. By the time my nephew and myself get in the row, and I put the fannypack, camera bag, etc. in the seat, there's not much room left. And it's not set up good to put your stuff on the floor. You put it in front of you on the floor and you're stepping on it. If you're on the "outside" side and put it on the floor, the server is stepping on it. We've never had a problem getting 3 rows when we're a party of 5.