G'day Stylo,
all the things you suggested make good sense (particularly the phone thing - I use an aquapac case). Basic rule is if it's not tied on (leashed) it's not yours. It's a rite of passage for kayak fishing that you will ignore this, and dump a rod (net/camera/etc) at the earliest opportunity.
I carry tackle boxes etc, but my kayak has a lot of room (hatches etc), probably best to minimise gear for the first few outings. A dry bag tied on to the kayak for tackle, keys wallet, phone is useful.
A PFD is mandatory (I'm an excellent swimmer, but still use mine every trip).
Trolling from a kayak is great, you'll need to work out a position for the rod that doesn't interfere with paddling (unless the kayak is a mirage drive). Stopping at any fishy water (I usually drift) is part of the fun.
