If they don't eat right away, don't panic. Leave the food for them overnight. Most of the time they will have been eaten by morning. Start with a fresh, full bottle of water and make sure bunny is drinking normally. If they seem reluctant to drink, try adding a little apple juice to the water, or consider replacing the water with Pedialyte which contains electrolytes to help prevent shock.
Some rabbits prefer to drink from a shallow dish after surgery to minimize their movements.
Provide some peace and quiet for your rabbit away from noisy children or other stressful situations for a day or two following surgery. Put them in a freshly cleaned cage even if they normally have free roam. A cage provides a safe haven from children or other pets, and will help you monitor any changes. It also keeps them from overdoing it. Keep an eye on how they are eating and eliminating.