It's a very personal decision that only you and your husband can make. However, my number 3 is 2 months old and so far I couldn't be happier that we've had 3, he's made us feel much more like a family
It took us a long time to make the decision and even when we started trying I still wasn't 100% sure it was the right choice but now he's here I know it was
My pros and cons were
Pros:
Dh and I both come from larger families (dh one of 3, me one of 5) so it seemed "the norm" to have more than 2
1&2 were both boys so was a chance to possibly have a girl and have the experience of both sexes (he was another boy so this became irrelevant)
Already had a big enough house
Supportive family who are happy to babysit regularly
I'm a sahm so no increase in childcare costs
ds1 would start school before baby born so I wouldn't have 3 full time at home
cons:
needed a bigger car
Holidays/day trips are more expensive/complicated with 3
More years in the baby/young children phase
More expensive
less time for the two we have
Possible special needs making the third more challenging than anticipated
I honestly would have a fourth if money was no object and if I was physically up to it but after 3 c sections I'm not prepared to put myself through it again. And obviously it's early days but so far I feel like having 3 has improved our family so much. I've found by the 3rd I just take it all in my stride, I'm used to the manic mornings getting everyone out the house, endless laundry and never feeling like I'm on top of the housework. A 3rd person in the mix really doesn't make much difference