We decided to tell them because DSS keeps asking me about my bloating in public and we have heard them talking about it together.
We told them that I have a baby in my tummy that is as small as a pea and hopefully it will keep growing and growing and come out to live with us when it is ready. We told them that it is a big family secret until we get a picture of the baby from an u/s and we also discussed the possibility of m/c.
They were so excited and they both understood the m/c thing and keeping a secret they were jumping around and yelling 'yay yay yay'.
At bedtime though, DSS(5) said he was a bit worried as '3 babies and 1 big sister is going to be a lot to look after' (his mum has a 2 yr old and a baby on the way), we discussed that they would be in different houses and that he wouldn't have to look after the baby at all. I hope he is going to be okay...he was definitely excited initially but obviously thought about how many siblings he would have in total. Maybe he is worried about whether his place in our family will be different or something too? I really don't know how to reassure him :S I wasn't prepared for him to be so worried!
On a positive note: we are all in agreement that we would love another little girl but obviously either will be lovely We all have our fingers crossed for a girl hehe!