I don't really have anything intelligent to add this morning - I used it up on my last response! I am still so tired and not yet had a morning cuppa.

I just wanted to add - if you look at my sig you will see that I am about to face your dilemma a third time and, honestly, I have no concerns at all. We have already helped DS3 learn how to say 'baby' when he sees friend's children that are younger than he is. Now and then when he is in 'cuddle-mode' I take his hand and put it on my belly and say 'Hello Baby'. He is still too little to really 'get-it' but will by the time I start to show more seriously.

For me inclusion of children in pregnancy is really important. I know for many they insist that children shouldn't be told until later because of the wait - but I wonder why shouldn't they learn that babies take a long time to be knitted together before they arrive in the world?

Just for reference for those who are watching - the age gaps I have had / will have are:

DS1 --> DS2 1 year 2.5 months
DS2 --> DS3 2 years 6.5 months
DS3 --> DC4 2 years 7 months

You can always wait 6 months and see how things are then.
Just so long as you keep in mind that there will then not be 9 months growing up in between but, rather, 15 months.

Seriously, my suggestion is to simply go with you heart - you know your DS best. Each of my boys (other than rough-housing with each other) are kind considerate children and they have been more than willing to show love to the new baby each time.

There are also lots of strategies I employed to give each 'no longer the youngest' child every chance for special time with me also as well as to make a special effort to provide engaging activities for them whilst I did need to tend to the newest addition. That is an after-morning-cuppa topic though!