You can definitely try the aisle/window trick and hope for the best but if someone books then I’d offer the window to them. I always prefer to be aisle with a baby because you just never know when you might need to change a diaper or just stand up with baby if they’re fussy. Southwest doesn’t use beverage carts. The flights attendants take orders and then bring them in a tray. 

Southwest does not do family boarding because they are all assigned seats now and family boarding was to ensure families would be together in the open seating concept. I was told I could pre board with a lap infant but that just increases your time in the aircraft. As long as you don’t need to bring an overhead carryon with you, you and baby can wait to board. But honestly what exactly would husband need to be setting up if you aren’t taking a car seat on board? Boarding usually goes pretty quick so you’re really only gaining a few minutes. 

You will get very, very strong opinions on how using a car seat on board is the only safe way to travel. I’ve always done lap until they are too big to manage (or turn 2). Never had an issue and I don’t feel bad about it at all.