It's a minor point but I doubt PBY's were used for level bombing and I'm going to dig around a bit to see just what was available on the first day. More likely it was carrier aircraft
EDIT: Found it......
http://pacific.valka.cz/forces/tf52.htm
TG 53.7 - Guam Landing 44/07 - 44/08
CTG RAdm Van H. Ragsdale, from 07/27 RAdm Thomas L. Sprague
CVE
CarDiv22 (RAdm Van H. Ragsdale):
Sangamon (CVEG-37: VF-37,VT-37)
Suwannee (CVEG-60: VF-60, VT-60)
Chenango (CVEG-35: VF-35, VT-35)
CarDiv24 (RAdm Felix B. Stump):
Corregidor/UF,DF (VC-41)
Coral Sea (VC-33)
Kalinin Bay (VC-3)
Absolute for certain there were Avengers on those carriers