Is it a SIN to wish health and happiness for others?

There is no clear cut list of sins.

 I think most people just reference the ten commandments.

 I feel like You are asking about "wishes".

 Following the idea that God would obviously be the entity granting the wish- You must also assume that god would not bestow anything undeserving.

 Ultimately You are leaving these requests up to god.

 I don't think it's a sin But, I do think if it were using god a middle man should clear up any personal involvement or responsibility. 

Shouldn't you do BOTH? Wishing/praying for health and happiness for others is a very nice thing as it displays a good intent of heart of an individual, but you have brains and ability to help as well. You should ACT and do your best. If you want God to help through you, you have to act. 

We can pray for others. Yes!

People have to make their own choices. You can't put that burden on yourself,  if others abuse their healthy bodies or enjoy a habit thats bad for them. Thats their freewill. You can hope or give them helpful information.  but leave it to that person to want to make the changes.

Acts 15:29to keep abstaining from things sacrificed to idols, from blood, from what is strangled, and from sexual immorality. If you carefully keep yourselves from these things, you will prosper. Good health to you!”

3 John 1:2Beloved one, I pray that in all things you continue to prosper and enjoy good health, just as you are now prospering

James 5:16Therefore, openly confess your sins to one another and pray for one another, so that you may be healed. A righteous man’s supplication has a powerful effect

JW.ORG

How dare you THINK?  You should only entertain an empty void in your mind, in order for it to be ready to be filled by divine inspiration.  If God wants you to have a thought, He'll provide it for you.

ONLY TRUE GOD IS YAHWEH THREE IN ONE...NO OF COURSE IT IS NOT WRONG..