There are a few suggestions:
1. It may be appropriate to invite his wife, and if possible, other family members such as sons and daughters, to be on the stage together with the retiring employee.
2. If so, say a few pleasant things about the wife and other family members, express your well wishes, good health, and present them with a bunch of flowers or a shawl (considering Bangalore, a Mysore turban). If the wife is willing and able, she can also be asked to say a few words.
3. The actual words of a farewell speech would depend on the nature of his duties and contributions. If you are eloquent in giving speeches, you would know how to make the function memorable.
4. You can also consider remembering a particular event or occasion in which the retiring person impressed everyone, which would be fitting for the occasion.
5. I hope you are preparing to present him with a memento or a gift. If so, you can add a few words signifying why you chose such a gift as the most appropriate for him.
6. Also, express your sincere apologies for any inconvenience caused to him during his service.
7. It would be appropriate to present a cheque for his full and final settlement/gratuity, a service certificate, and a special Appreciation Letter on the occasion itself. If he is eligible for a pension or a parting gift from the management, you may present its orders/gift cheque.
8. It is also fitting for a few of you to accompany or drop him/them in your office car at his house and depart after sharing tea at his house.
9. Add a few words to convey that he shouldn't feel he is 'out of office' from the very next day but is always welcome to visit as much as possible.
10. You might as well host a high tea (if in the evening) or a lunch or dinner followed by a group photo. A framed copy of the photo, signed by your CEO, could be sent to his house.
I also join you in wishing him all the very best.