My family doesn't love the entrees at Sci-Fi, but we do enjoy the appetizers and we LOVE the atmosphere. So we don't order meals, just apps. Have everyone order a soda or milk shake ($6x5 people = $30) and then spend up to $65 on apps to share and you're at $95 leaving enough for tax and a reasonable tip. Our bill for 5 people is usually around $70 plus a $20 tip so the server doesn't get short changed for our food preference.
If you want to order entrees, it's definitely doable if the adults stick the $14-15 range plus a soda, or have water. As someone else mentioned, if your bill comes to $95, the remaining balance will cover tax and tip. Assuming the child chooses the most expensive kids meal at $12 (includes a drink) that leaves $20.75 per adult. Ask everyone to bring a bit of cash that one day, then anyone who wants to order above their $20.75 can pay cash for the difference and add a dollar or two to the tip.