We will be attending our second Gen Con but first with Kids this year. Many of the events say everyone (6+), however, my son won't be 6 until September. I figure he can pass for a 6yr old but my daughter will be 4 in September and wondering if she can "tag along" for an event like Fairy Games for Mortals. 

I figure she can attend the craft events but just needs help from mom and dad. Also, I'm guessing she needs a ticket for the event regardless? 

Any event suggestions for young kids? We are just happy to be going and are keeping expectations low as far as any actual gaming we may get to do. 

Thanks!

The event you named specifically says ages 8+. You should probably email the host and ask whether bringing the 3yo is appropriate.

The KIDS category lets you buy event tickets in the name of someone who has a wristband rather than a badge.

Otherwise the age limits are guidelines. We've run LARPs as 18+ not because of adult content, but because they had romance plotlines and we weren't comfortable pairing off an adult with an adolescent.
Many events at Gen Con require the ability to read, or to pay attention for several hours, or to handle scissors. Kids under the "minimum age" are allowed if they are capable of participating correctly and won't ruin the event for everyone else.