Dear Zahida,
It is a nice attempt from your side to make the employee feel special on his / her birthday. I am sure you can add a couple of other things to make the occasion more special.
1. Put a copy of the card on NOTICE BOARD.
2. If you have a cafeteria, Put a banner wishing the person.
3. Have Monthly birthday celebrations, incase there is budget constrain.
4. Invite the spouse of the employees whose birthday is celebrated.
5. With the card, give a flower /bunch of flowers etc...this makes them feel special.
6. Have the Head of the firm / Head of the department send a mail to employees wishing them on their day.
7. Have regular mailers to the team regarding the up-coming birthdays of the month.
These initiatives will make the employee feel that he/she is taken care of by the company.
Regards,
Arun