Thank you so much for helpful suggestions above.

I will check out with the dive shop that I get a gear rent to have a divemaster out for the first dive tour to check the conditions, environment and additional skill I need. My concerns will be on the next dives or the next day if I want do the boat dive. Would the boat has a dive master or can pair me up with someone on the trip? And if they allow diving in group or a buddy can find on the shore there? I believe that it will be crowded on the island during the memorial day weekend.
The divemaster would pair you up if you don't have a buddy. You will find that most SoCal divers are very friendly and don't mind taking a visitor under their wings.
I used to dive with 5mm wetsuit for 5 dives, and familiar with weight checking so thickness shouldn’t be much trouble. Setting up equipment and helping up myself with lot of weight shouldn’t be a problem as I’m male, 6’ and 175 lbs. Also 5 out of my 9 dives had visibility around 10-15 feet. Cold water and kelp entangle are what I concern more.
You've already dived with a 5-mil suit and know how to do weight check, so the 7mm suit isn't going to be all that unfamiliar to you.
As far as diving in cold water with a wetsuit, there's a lady whom I dive with from time to time. She's barely 5-ft tall and maybe 90-lbs soaking wet. She dives in the coldest winter day with a 7mm wetsuit and a 3mm liner.
Anyway, as far as kelp entanglement goes, it's not that big of a deal. First of all, don't carry anything that you don't need to carry on your BC or your body. One small flashlight is fine for day time diving. You don't need a death ray laser PLUS a backup. If you're not diving in blue water, then ditch the SMB/Safety Sausage & reel. If you don't need a big knife to kill JAWS with? Leave it behind.
Then when you dive, you pick your way so that you don't have to go into the thick of the kelps. If you get entangled underwater, just stop and don't struggle. Feel your hand around until you find the kelp and snap it. It's really easy to snap the kelp with your hands. If you're on the surface, don't try to swim over the kelp. Dive down 5-ft and go underneath the kelp canopy. BUT if you really, really, really have to swim on the surface, then swim on your belly with your face down and use your snorkel/regulator. Push the kelps down and away from your body (aka The Kelp Crawl). Swimming on your back through the kelps simply doesn't work. Whatever you do, don't twist and twirl - that's a good way of getting kelp wrapped around you.