TBH that sounds EXTREMELY expensive for a cake for that amount of people - now I dont live in Melb so am not familiar with those particular cake shops, but over here in Perth under $100 will get you an amazing cake for that amount of people.

I come from a big European family so have seen lots of different christening cakes but at the end of the day most of them have a cross, the childs name and the christening date on them. They dont have to be too elaborate at all.

The cross does sound lovely tho.