I've gone through intros with a baby twice now so I can share my experience.
DS who was 10 months went like this :
First meeting was just for an hour.
Second day was half a day at the FC's house.
Third day was whole day at FC house with us taking DS out for a walk in the buggy for a couple of hours.
Fourth day was an early start with us giving DS breakfast lunch and dinner and doing bed time routine.
Fifth day was FC bringing him to our house and leaving him with us once he had settled. We had him all day and then took him back to FC house and did bedtime routine again.
6th day - drive over very early to FC house to wake DS up , get him ready and bring him to our house for the day and then back to FC for bedtime routine
7th day - morning only at FC house to give everyone a little break.
8th day - FC brought him to our house and we all had a meeting with the social workers to check that all was ok for placement to happen the next day.
9th day - we collect DS from FC house and take him home for good.
FC visited after two weeks and then wasn't allowed to see him for three months. We took him to see FC regularly after that but recently he has refused to see her and gets quite angry if we suggest a visit. He believes she doesn't want to see him which is absolutely not the case.
DS really felt the loss of his FC and had night terrors , terrible tantrums , tried to hurt himself and even now , at 12 years old ,has a deep fear of change and has feelings of rejection. He has had to have therapy and counselling and I honestly believe that most of his problems stem from his feelings after being separated from his FC.
DD was also 10 months but her intros were taken more slowly.
It followed the same pattern as above but went on for two weeks. Things were taken at a much slower pace.
Also we were advised that it was now best practice for the FC to retain some regular contact with DD so that she doesn't just disappear from her life.
DD settled in really well and still has a great relationship with her FC who has become a good friend to me and our family.
DD has so far ( now almost 10) not had any problems or issues relating to her adoption. She is a very happy little girl with none of the insecurities common in adopted children.
Now this could all be down to their differing personalities -
DS was a very advanced baby - was already walking and talking at 10 months. He is very bright and seemed much older than 10 months ( many people , including my heath visitor .mistook him for a two year old) I think he was much more aware of what was happening to him than your average 10 month old and this may have caused some problems.
DD is and always has been very behind in her development. At 10 months she looked and acted like a 6 month old. She has always been happy and content in her own little world. I think that she was far less aware of what was happening to her and fared better as a result.
So who really knows what is best?
It's a tough one but my advice , based on my limited experience is to take it slow and make sure your existing DC is included in the process as much as possible.
Whatever happens I hope it works out well for you all. Congratulations 