Do people having 2-3 years of work experience doing PGPs at IIM Ahmedabad get decent packages or bigger packages than freshers?

Whether people with and without work experience are offered different packages actually depends on the sector and scenario.

For example during the Summer Internship, candidates of a specific sector (Consulting, Marketing) everyone is offered the same package except for a few companies that ask for experienced candidates only. People with around 20 months of experience are eligible for Laterals Process. 

Sometimes only within a particular sector, do people with work experience get better jobs than people with no experience.

But during Finals process, there are usually no distinctions between a person with work ex and a fresher