NO! To everyone!
Never you an online translator to translate from or to Welsh or English; the Welsh language is a rich and complex language, with many words sounding the same to a non-Welsh speaker, but all having their subtle differences; yn, mewn, i mewn (and others) all mean 'in' in a loose sense, but ALL are used in different contexts. An online translator of Celtic languages will just have the one version of 'in,' which, more often than not, will be the incorrect version needed for a specific translation.
For even just THAT reason, online Welsh-English translators shouldn't be used. But there's also the mutations, word orders, idioms etc which aren't found in English.This one
is complete rubbish. Don't even bother, as you'll look like a fool to Welsh speakers, as someone found out when I told them what the translation of THAT website meant - almost all gibberish.Geiriadur.net
is a dictionary translator, not a text-paragraph translator. When in doubt, I cross check this one with the BBC's
The only possible one that seems of any use and 'correctness' is a project translator being done by apertium-cy, which can be found here
(see the direct right side for the English language pages).
But please, don't go using ANY translation taken from an automatic online translator for the Celtic languages, especially in any official Grove or Coven documents; get a native speaker to translate it.