How do I go about setting up a 'Merry Christmas' wallet for my bride; and yet another 'Christmas present wallet' for my daughter. Three separate wallets—each with a unique seed.
The only distinguishing factor between wallets is the seed itself, as you have described in your original post. The wallet program itself has nothing to do with giving separate gifts to separate people.
From there, thinking of ways to package the seeds to make them feel personal, I would imagine that a hardware solution would be ideal. Essentially, generate 2 new seeds and save each one in a password manager such as Keepass, with a password your bride and daughter would know, respectively.
Then, save that password database with the seed inside onto a Christmas/gift themed USB drive. Possibly include other fun images or memorable files on the drive for more fun.
From there, I would also recommend uploading the password databases to the cloud and also kept on any other digital storage mediums you have such as PCs or backup hard drives you have in your house just in case.
Finally, log into each seed with your wallet and create addresses, then log into your original wallet and send the desired amount of gift iota to those addresses.
With that, your bride and daughter will both have their seeds which is all they need to access their IOTA from any wallet, anywhere.
PS: I would highly recommend putting together a basic guide on how IOTA is used safely, and what to avoid, such as sharing seeds.