We just threw a party for our daughter's 7th birthday last weekend with 2 of her classmates who are also winter babies. The cost was less than 100 euro per family including a full lunch, drinks for the grownups and rental of the school as a party venue. For entertainment my older daughter (aged 10) painted all the kids faces, I bought a pinata (7 euro for the pinata plus around 6 euro for candy) and the kids used sidewalk chalk in the school courtyard and played basketball. I made cupcakes with my kids for the party but the two other families bought cakes for their kids.