I have an old sears 12' aluminum. I was very skeptical at first as well about boating in the larger lakes and sound. If I were you, I would start on smaller lakes where gas motors are prohibited. I live in south king county and there are many lakes around here that are perfect, north, geneva, star, dollof, kilarney, steel and many others. By doing this, you will know about how long your electric motor/battery will last. Then after you are comfortable with how the boat handles in different conditions, get that gas motor going and hit lakes like angle, meridian, wilderness, sawyer. As you get even more comfortable with the bigger lakes and more boat traffic, you can then step it up to lakes like american, riffe etc. Like many others have said, just be aware of your surroundings and weather conditions. Dangers will come at you from everywhere once you hit the larger lakes. The more open water you face, the more the wind will become a factor, so stay close to shore until you get comfortable. Also, the bigger lakes tend to have more boat traffic, and they will ALWAYS try to pass within 20 ft of you. Make sure you stay aware and try to go bow first into the wakes. I should also mention that you should know both you, and your boats limitations. I would only recommend 2 adults in that small of a boat, maybe 1 adult and 2 children. If you do bring others out, make sure that they know that they should not make sudden moves or leans side to side. I can't tell you how many people I have brought out that get excited about their first fish, and lean over to see it, nearly tipping us. I would also keep life jackets available for every person on board. Also, keep many modes of propulsion, meaning, oars, electric motor, gas motor etc. After a little practice, you will see that your boat will be more than capable to handle the local lakes, even the bigger ones.
About the sound. I have been out a few times this year, but you will have to keep a few things in mind. DO NOT go out if there is any wind what so ever. I would only go out on the calmest of days. You also have to remember currents. If you don't have enough power, i.e. good gas motor, you will get pulled all over. I usually try to go out around slack tide to try and minimize these effects. As others have said, I think that your biggest enemy out there is going to be other boats. You will see many other bigger boats, and they will throw some large wakes. Again, be very aware of what is going on around you. If you do decide to go out, start out by staying close to shore. You should not get farther from shore than you are comfortable swimming. Other things to be aware of on the sound are Coast Guard rules. You should have CG approved life-jackets, oars, a signalling device (whistle, flares, etc), capacity plate, and others. If you are on the sound, you will eventually be checked, but these things are required for a reason. If you get spooked or aren't comfortable, don't go out on the water and wait for another day. I'm sure that I have forgotten to mention something, but this should help for now. Just remember to be as safe as possible and keep your head on a swivel. You will be fine out there. Have fun and enjoy your boat!