Please help me need some in sight on it to help me wih everything that could be thought of :) thanks guys :) *?

Ok I got a hard choice to make! I have a 4 yr old son, and my husband has a 3 yr old daughter, and a 2 yr old daughter( we have 3 kids) we are 20 wks pregnant, and we don't know if we want to get my tubes tied or not?? For 1 reason if it's a girl his name dies by blood, but will be carried by my son, and for 2 this baby will be the only we had together! But also it's FOUR kids lol and if we deside to have another that's FIVE!!! Lol that's 5 driver eds, 5 first cars, 5 colleges! It's just hard on us to choose, but we have to have it chosen and a paper sighed by a certain time for medicaid to pay! Just want some more brains thoughts to help thank you