Hi there.
I did the SilverSonic Boxing Day.
My review is on Trip Advisor
here including some photos I took (including one the guide Erin took of me).
I would recommend the SilverSonic above going out to the pontoon for the simple reason that it is smaller - much smaller.
I can't comment on the diving or snorkelling at the pontoon, but the stops we did on the SilverSonic were very enjoyable. None of the dives were complicated/challenging so your daughter as a novice diver will have no issues.
They had a very good ratio of divers to guide/divemaster when I was on board. 1 guide to 6 qualified divers. In our group there were 5 plus the guide. Our guide Erin was excellent, and I suspect similar to the other guides. She was very focused on safety and always aware of the location and situation of her divers. She also made sure we all saw as much as possible on the reef. All my dives hit the max bottom time of 50 minutes.
I did all three dives, and while the first two seemed a little squished together, you are there to dive, not to lounge around on deck... unless that is what you have signed on to do.
They had lots of noodles for the snorkelers and a look out on deck at all times for them.
One thing I noted was that they took people into the water who were not strong swimmers and they kept a snorkel guide in the water with them. Those that got tired, the tender went and got them.
I highly recommend this group and look forward to diving with them again soon (though to be honest my next dive trip out of Cairns is the Osprey Reef trip with Mike Ball).
Taez