When to tell my son?

TS

Hi all, just recently found out I’m pregnant (almost 5 weeks). Super excited as I’ve been trying for my second for 2.5 years!

I have an almost 6 year old that I’m dying to tell he will be a big brother (he’s going to be so so excited) but I also don’t want him blurting it to others!

Any advice on when/how to tell older siblings? Thanks in advance!