When should I send the party invites out??

[Allthreerolledintoone]

Ds birthday is on Saturday 18th January. They break up from school next week and return on the Tuesday 7th January so do I send the invites before the holidays?? Or when they come back even though it's less notice.

I would do first day back, before Xmas it's just asking to be lost or forgotten about replying with everything going on.