Watermelons and pumpkins and various other winter squash run where they wish. You can cover several hundred square feet with a couple of hubbard squash, the way they spread. And the vines can be moved when they go where you don't want them. A friend covers part of his front yard with three plants.
I wouldn't worry about companion planting those two, but that's just me. The seasons don't match up well for me. Another challenge is the grandchildren. They'll 'help', if allowed to play in the garden, and, of course, they're allowed to play in the garden. So the melons are a little iffy, here. Good thing we can buy good ones cheaply in season.