Morning Pippa mate,
Here's my tuppence worth (for what it's worth).
At the end of the day they are your children, you and Mr Pipps are their main carers and will be brought up in the best way that you two see fit.
Obviously grandparents are important and their views should be taken into consideration, however, it's up to you to celebrate (or not) in the way you both want.
P.S if you do bake a cake, can I have a piece, unless you use marzipan, I hate marzipan
and Brussels sprouts
and I don't like dogs either
or wasps