You'd better to check your state law, if over 18 weeks....

You need to check with OB doctors to make sure all legal. 

I fully understand that only 2 of you to take care of kids.  It's really difficulty to take care of 3.  Since your 2 kids are young.  When in middle and high school age, you need to send them to learn piano, swim, other sport.  You will spend money and time.  When they are in college, you will find out no money saving for your retirement.

I really suggest to save the new comer's life.  You need think twice then make sure that's right decision. 

God bless you and your family.