My 3.5 year old daughter had the inactive vaccine (the spray is live). I got her vaccinated this year because she's around my dad a lot and he's immunosuppressed due to chemotherapy. No ill effects. We went for the inactive vaccine rather than the spray so that she didn't have to stay away from my dad for 3 weeks afterwards or that she'd cause problems for my son (who's too young to have either).
However, I did decline it last year as I couldn't see the benefit. She only had it this year because of dad and if he'd been fit enough to have the flu vaccine, I wouldn't have vaccinated my daughter.