Yes, it's super fun! We take both my kids bowling (5 and 3) and they love it! We did attend a bowling party a year or so ago and it was great, all the kids were about that age.
Bumpers are a must though. Some alleys have ramps that are used for handicapped people to bowl but sometimes they allow kids to use them, it just depends upon the facility.
I will say though that you need to have plenty of adults around to help. They get distracted easily, climb all over the ball holders, run around, etc. Plus, some kids might need help, even with the bumpers.