OP, We have 4 DC, but the biggest shift was going from 2 to 3. I would say the main reason for this is that the permutations for the “dynamics” between your DC will double (at least)!
There is a big difference to the “vibe” and family dynamic of having a group of DC, as opposed to a pair.
For instance, a pair of DC may hit it off and be very close going into adult life. But it’s also quite easy to not be that close if they are just very different or just not that way inclined. So they can be quite indifferent to each other if it suits them.
Howver, the third one can often be the agent that kind of binds them all together (for better or worse) - simply because nobody likes to be the outsider in a group. This is human nature. Nobody wants to feel sidelined by the other two, so there is a whole new dynamic of rivalry to contend with.
It takes a lot more headspace and emotional energy to meet the needs of 3 than 2. In fact, I would say the emotional load doubles.
The plus side is, it’s never boring! Nothing is ever dull and the DC occupy each other far better than if it’s just two. Your DC will always have each other and be able to share the stresses of life going forward as a team - eg. parents getting older. Their DC likely to have more cousins and there’s a sense of strength and identity that can come with that.
You obviously don’t feel “done” yet so I wouid say, as long as you can afford it, go for it. Life is too short for regrets.