I like Sony HD MiniDV (HDV) Handycam Camcorder - HDRFX1000, but I have also used several older Sony (DCR-TRV17 and DCR-TRV70) and Canon (VIXIA HV20, VIXIA HV30, and VIXIA HV40) tape-based Firewire-equipped camcorders with good results.
I prefer tape-based Firewire-equipped cameras because of their IEEE 1394 transfer speed, compatibility with iMovie HD, and ability to serve as the source recording directlyinto iMovie when desired. If none of these characteristics is important to you, other Mac-compatible camcorders with suitable zoom ranges and lens speeds for the light levels you encounter should also do nicely for recording at your games.
You do not say which iMovie version you are using, but you can find about known compatible camcorders by searching for the info in a search like this one.
Message was edited by: EZ Jim
Mac OSX 10.9