KPEG, first let me say to you breath. Just breath. One thing I am learning in life right now with the struggle that I am going through is, just take a moment for yourself. With that said, I don't think that you should be feeling guilty about your DW. Life does happen, things do occur, changes take place all the time. But ask yourself these questions, when you and your FI first announced that you were having a DW and everyone was excited about it:
(1) Did your in-laws need visas and passports?
(2) Were your parents working at the same jobs?
(3) Was your brother attending school?
(4) Did your sister agree to come with the knowledge that at the point she would have a child?
From what you've said, the changes that have occurred are your cousin's wedding and the houses being built. As family when we make a commitment to each other, that is exactly what it is, a commitment. And even though all the factors that you mentioned above existed everyone told you they would attend. You shouldn't try to carry everyone's load for them, you can only carry your own. If your parents didnt want to take the time off work, then they will tell you. If your sister thought it would be a hassle to travel with the baby, then I think she would have said. But it sounds like your family loves you and even though things are rough sometimes, they will be there.
You have enough going on building a house, planning a wedding, work, and just life. Everything that you have said makes complete sense and you do have to think about other people. But if they have an issue with it, then they should say. If they don't then just let things be. As to your estranged uncle, just apologize to your dad and ask him if he has the address (sometimes eating crow is what we have to do to keep the peace even though we are not in the wrong).
Hope I didn't go on to long
A