Awesome to hear @xLAKITUx extra storage is always welcome for backup purposes. I don't think you should run into any problems with the SD upgrade. I recently mod a neighbor's Wii and another for my brother & they are using Verbatim 16GB SDHC SD. I did all normal emulators setup on WFL (Atari 2600, 7800, Sega SG, GG, MS, MD, TG16, Nintendo GB, GBC, GBA, NES, SNES, Coleco) with a few Wii & WiiWare EmuNand. Both are still working afaik. Huge MKW fan & used to play CTGP on nightly basis until my SD went down. I played Wiimms distributions for a few years as well as making a few of my own for personal use I still have on my HDD. I was given a Verbatim SDHC SD & have 2 perfectly working Wii's stored away. Maybe I'll see what's new on the CTGP scene too.
and I’m correct in thinking that if I just copy the contents of both drives onto new ones (assuming they are both formatted as FAT32 with 32k clusters), it should work with no extra steps?