If you are new to California and kelp the water is usually 50-60 degrees. Colder in low 50's during winter and also the deeper you dive. I've heard reports recently water has been unusually warm, just around 60 degrees. In addition to your 7 mm wetsuit you will probably need hood, gloves, and booties.
Not all hoods are the same. Some are more stretchy than others. You should really try different ones on for comfort. My daughter intentionally dives with a hood larger than recommended baecause she can't stand the tight claustrophobic sensation if it is any tighter.
I've also removed my gloves from time to time and water can feel like ice water. Although the temps don't sound too cold your fingers will go numb in few minutes without gloves. 3 mm are most common but I actually prefer a 4 mm thickness since are slightly warmer.
When buying boots take you fins with you, assuming they are pocket style and not full foot. A 5 mm boot is just fine.
I also like to discuss common hand signals with instabuddy divers, especially the critters you might see. There some cool signals for lobster, octopus, and nudibranchs. I also like to discuss how you indicate tank pressure in particular, then quick discussion buddy separation. Can be as innocuous as, "how do you signal 1300 versus 1800 PSI, and what do you want me to do if we get separated."
I did get separated from an instabuddy once who got paired with me and my buddy who happens to be a newbie. We did a swim through some kelp, looked back, saw my buddy but not the instabuddy. We tried back tracking little bit, swam toward and area thought he went, then surfaced. We saw him about 30 yards off. Turn out as we started through some kelp there was bother group of divers near us, one with similar colored yellow fins. He followed wrong set of fins. Once he realized his mistake he couldn't see us a didn't know which direction we had gone so he decided to wait for us on the surface. We didn't really discuss this but surfaced within less than a minute of each other.
As far as your weights, I'm about 140 lbs. I will use between 18-22 lbs. depending on the dive and who I'm with. I tend to go heavier with my daughter and lighter with more experienced divers. General calculation is 10% body weight + 5-7 lbs. that gets you to a ball park but you should do formal weight check prior to your dive. Discuss with your buddy you are new, haven't used a wetsuit that thick, and will be doing weight check before first dive. Try having all your gear set up early just before you arrive dive spot so all you need to do is finish getting hood and gloves on. Then get into your gear and try to be one of first divers into the water. Crew can help you by either giving or taking weights as needed since you should still be next to boat. By the time your buddy gets in you should be close to finishing weight check. Better 2 lbs heavy than too light and you can always take off before next dive.