We have twin girls turning 4 next month too. We have a large family also. It gets a little stressful. With just our families we have a hard time inviting our friends it's just so many people.
Last year we did an egg hunt party at our house. The girls birthday was on Easter. It was a lot of fun.
We have 5 children and have to do parties super cheap. I always get the paper goods and a few decorations at the dollar store. We NEVER do goody bags, except last year I did the stuffed eggs. I got all the egg stuff at the dollar store. Sometimes we do food, but ususally we don't. If we do food, I get the frozen lazagnes and garlic bread from Costco. It's about $30.00 for 4 lazagnes and the garlic bread and a bag salad. I ususally make the cake or cupcakes myself. Cupcakes are easiest. It usually costs about $4 or $5 to make cupcakes with frosting. I don't serve alcohol or soda. Just water and coffee. We have a water filter pitcher so I don't buy water.
I have got it down to around $50.00 per party, and thats if I make food. If I don't make food, I can do it for about $20 or $30. We usually have between 30 to 50 pepople, including kids.
Hope this helps.
EDITED TO ADD: I always take advatage of the few that say "can I bring something" YES you can. I aks this person/people to bring an appitizer like chips and dip or something.