as the author of ModMii I'm obliged to inform you my opinion is biased, but yes, I would say this is the best way to mod your Wii
As long as u follow the instructions to the letter, the only risk you face is the risk of power failure during the installation of a couple crucial files... and those file(s) only take 10-30 seconds to install so chances of losing power at the exact wrong moment are very slim... and even if it somehow happens u can recover easily if u were able to have bootmii installed @ boot2, and even if u don't u can recover using an infectus modchip (assuming u made a nand backup already, which ModMii woulda instructed u to do before installing those crucial files I mentioned above)
long story short, 7 year olds have successfully modded Wii's using ModMii (might have been 6 years old, I can't remember right now). And another success story was received by someone over the age of 60. It really doesn't matter how technically competent u are, ModMii allows anyone to unlock their Wii.