If you are looking for a source of Welsh language letters from the man in red for your little ones, then look no further than the NSPCC. We’ve been using them for some years now and have always been very pleased with the results.
The NSPCC Santa letters are well made, fun and come with plenty of age appropriate, beautiful illustration choices. You can personalise your letter with information about your child and with no mention of gifts, which I think is great.
A letter requires a minimum of £5 donation to the charity, which I think is well worth it.
Follow the below link and at the bottom of the second page, where you make your choices and personalise your letter, you can choose Welsh as a language.