To work with various formats of footage in a sequence without rendering you need to capture all the footage using the same codec.
First off, DVCAM and MiniDv is exactly the same format…DV/NTSC. The only issue is working with it in an HDV timeline. HDV and DV don’t mix, and I don’t think you can convert DV into HDV given it’s MPEG-2 compression.
Best solution? Capture your HDV footage as DV and work in a DV timeline. DV upconverted to 1080i will look really bad…taking a 720×480 image and resizing to 1920×1080.
If you are going to mix the two, work in a DV timeline. The cameras and decks downconvert on the fly.
Or get a capture card and decks capture both at a different format entirely, like DVCPRO HD.
(Who said editing was easy?)