Shri yemcee sir,
You may have the annaprasanam performed in any temple nearby in which they will do this. Or, you can sicerely pray for your grandson before your pooja in your prayer room, offer paalpaayasam as naivedyam and then give a teaspoonful to your grandson. Besides all these, you have many Vaadhyars in Jayanagar area and you may approach any one of them and they will perform this. The choice is yours.