1. I will extend the groundfloor toilet to the wash area and vent to backlane. Access utility from the dinning. Ill even consider to access toilet from dinning> utility > toilet.

Knock the kitchen dinning wall to make one open space with island/peninsula in btw.

2. I will remodel the masterbedroom toilet to the side. Not hard as you are already doing a whole new room above your porch. the existing toilet will be a good spot for walking closet. Also, brand new toilet in your master will be a highlight

3. for the 2 smaller bathroom remodelling, I will hesitate to touch cause U are gaining only little usable squarefoot but the work will be huge. I will leave it and spend the money just on re-tiling, changing the vanity and toilet bowl. give them refresh but not total remodel.

By the way, nice house! do update us on the progress

and also, 300k can do a lots of work with the size of your new house. With these money, I will suggest to hire a good architect that can help you in all the facilitate, including wet work and interior design. Save your time and your money!