Hi Yb,
Leave the AP mode as IAP. Campus mode relates to APs with a local controller architecture.
Upgrading software of the APs will be very simple once they are adopted into Aruba Central. AOS 8 and AOS 10 versions will be available to you. If your requirements are compatible with AOS 10 then my suggestion would be to the latest available 10 version (currently 10.4.1.0). Otherwise the latest available 8 version (currently 8.11.2.1).
In regards to the management VLAN on the AP you may not need to configure anything, this depends on how the switch port is configured for VLAN 1. If VLAN 1 packets reach the AP untagged (no 802.1q tags) then the AP will deal with the packets correctly. VLAN 1 is assumed in the software.
Good luck.