My cousin married an Australian back in Melbourne earlier this year. Our family decided to throw a small reception party for them when they were visiting Delhi. After a careful search of wedding venues, we finally chose Indira International Inn, Vasant Kunj. The reason for choosing it was its proximity to the airport (as many people were flying down to Delhi from Australia and Chandigarh).
Let me caution you that the garden is not very big in size. At best, it can accommodate up to 200-220 guests at a time. We had just about 150 guests, perfectly suiting our needs. They do allow catering service other than their in-house team. But on our special request, the in-house team itself made a menu that would be liked by our foreign guests yet give them a taste of India. It was done very well. The management took care of all details diligently.
We had also booked around 7 rooms for some of the outstation guests. They had no complaints whatsoever.