Cupcakes?
Dull, yet keep well, no raw egg issues, and can be dressed up to look pretty - if it's a girl, do vanilla cupcakes with pink frosting, pile 'em on a plate and decorate with petals or ribbons or girly frilly stuff, if it's a boy, chocolate cupcakes with cream frosting, or ice the letters of his name on them and arrange on an ENORMOUS platter with plain iced ones surrounding.
You'll get better ideas than that on presentation, I'm sure, but at least you can do it a day before, and it looks like much more effort than it really is.
Alternatively, buy shop bought, two fingers to the family, and excuse yourself by saying "pudding doesn't travel well, and I wasn't sure the fridge capacity was up to it".
Like any other similar situation, most of the stress comes from ourselves - presumably you won't be strolling round the gathering judging the seasoning in the egg sandwiches? Your pud will be welcome, whatever it is, if you have a sane family, and if they're not sane, don't break a sweat for them
Hope you have a great time, you may just have the weather for it, too.