Aside from overcrowding, the biggest problem may be past/disease issues. If, for instance, you have summer squash and pumpkins together, when the zukes start to decline, they become more vulnerable to powdery mildew. This will then be close to your pumpkins and winter squash, and may infect them as well. In a small garden, this is an issue no matter what you do, but any separation helps to reduce the likelihood. You should direct the vines to grow within the rows as much as possible.

And don't plan to save the seeds for future use as you will have lots of cross pollination happening there.

Otherwise it can be done if necessary but is far from ideal and harvesting will be very difficult.

Have you considered some large containers spaced well away from each other as an alternative for some of them?

Dave