I'm with all the posters who said it's just time to bow out of the exchange. Tell everyone now that you won't be buying and prefer not to receive gifts. Period. Don't give them an explanation to argue with. Just stick to your guns.
It's not fun at first. We did this years ago with both DH & My families because it was just crazy expensive buying for so many people. Especially when you don't know them all well and end up buying them things they don't want/need. It honestly wasn't even fun anymore.
I talked to my sisters and most of them felt the same way (all but one who lives further away and wanted to buy for all the nieces and nephews she gets to see so infrequently

). So, my family changed the way we did gifts to suit everyone. Instead of buying for all the kids, we exchanged names. To appease the sister who wanted to buy for all, we agreed to a $1 stocking stuffer for each of the kids' stockings. My shopping budget dropped from $200 to $40 that year so I was thrilled. (The stocking stuffer idea has held out despite the fact that the kids are becoming teens now. Sometimes we spend a little more than $1, but we have fun with the challenge of finding gifts for as close to that as we can get.

)
In DH's family, no one wanted to make a change. So, we just "opted out" of the exchange and told everyone we were. The first year, several family members bought gifts for us and that was uncomfortable to say the least. (But, we survived.)
The following year another family group followed our example and opted out.

This took a lot of pressure off. It was another five years or so until the final aunt quit buying for everyone, but I was long past being embarassed about it by that point.
Just get it over with. Tell them you can't do it anymore and stick to it. They will feel how they are going to feel and you can't change that.
Good Luck. And enjoy the Holidays and your new baby!!