|How important is it to keep pumpkins away from cucumbers and melons, and even different types of pumpkins (carving vs. baby boos)?
|It is only important if you plan to save the seeds at the end of the season, and plant them next year. If you use seeds that have been cross-pollinated, you may end up with strange pumpkin/squash/melon mix.
There is no need to isolate your plantsif you are not planning to save seeds. Cross-pollination will not affect this year's crop. The only exception might be if you plan to save and roast your pumpkin's seeds--cross pollination may affect their taste somewhat.