Yes, it is perfectly acceptable to say "loads of happiness." The phrase "loads of" is an informal expression that means a large or abundant amount of something. When used with "happiness," it conveys the idea of a substantial or significant amount of happiness.
For example:
- "Wishing you loads of happiness on your birthday!"
- "Her face lit up with loads of happiness when she saw the surprise."
This phrase is commonly used in spoken language and informal writing to emphasize a heartfelt wish or describe a genuinely joyous moment. It adds a sense of enthusiasm and positivity to the statement.