Bearing in mind that your income is going to drop, I personally would do something different entirely. Instead of a last hurrah I would pop at least half the money into a fixed term savings account to spend on a Disney holiday when the kids are older.
Babies are relatively cheap to travel with but the costs of a child catches up way before the cute little parasites start paying their way. Imagine how nice it'll be in 5 years time to suddenly have some spare cash for them to go and hug Mickey, just as they become aware of ads and start asking to see the castle.
Personally with a young baby I would go for a nice easy 5 star all inclusive resort in Europe that has some interesting day trips nearby. I would take it in turns to sleep and read whilst the other parent entertains the relatively immobile baby. I would enjoy their naps and the adult time they offer. I would relish being able to go for a long walk with the buggy or sling any time of the day or night if they're poorly or unsettled. But that's just me. Conversely if money were no object I would be on the
Disney cruise every time.
Whatever you chose you'll enjoy as you have no way of knowing for certain how the other option would have planned out. Have fun and enjoy your first family holiday.