Hi,
Firstly, sorry to hear of your bad news.
Secondly, it's important to realise that you can't just transliterate one language into another, and the Spanish simply don't use the phrase "give him my love" - it would just sound weird.
Instead, you will need to find a Spanish phrase which encapsulates what you are trying to convey and, I think, in this instance you would want to tell your mother-in-law that her husband is in your thoughts.
So, you might like to consider something like "le dicen que está en mis pensamientos".
Finally, steer very far away from online translation sites - they are all, without exception, worse than useless...