I think if you are financially secure and you already have a toddler I don’t think it will be that big a leap for another.
I would worry going forward that the older 2 will eventually cut out this younger sibling and I would want to give the younger sibling at least an ally
I understand not all children get on but it is rare for dc with larger age gaps to be that close as they will forever be at different stages in their lives.
You are still in the baby/small child phase and it isn’t much of a leap to having another now.
Why are you embarrassed about being pregnant?
I think you need to embrace this pregnancy and be positive. If you give a hint that you are embarrassed or not really wanting to be pregnant then your dc will pick up on it and this child will start off in life with siblings who think that they are an inconvenience and not wanted.
For me I would look at the dynamics of the family
ATM you have 2 children that are older and 1 which is for all intents and purposes is an only child but an only child with uninterested siblings which gets more complicated growing up
ATM we are dealing with dh’s older sibling who has single handedly cut Dh from everything to do with his parents.
Because Dh is younger he has always been ignored.
BIL acts like he is an only child and will fudge and lie to make it look like he is the only child. He is in his 70s.
I have seen similar happen to other families with large age gaps
At least where there are a couple of children in each age gap they can’t be ignored.