@Jagreenaud06this is so exciting! I think you will love to have your family with you out on the water.
First, if you haven't read the article on choosing a kayak , take a few minutes and check it out. Using a sit-on-top kayak is going to be your best option. As your three-year old grows, I think it also makes sense to use a tandem like Ocean Kayak Malibu Two or this Perecption Pescador. There might be a concern about the kiddo tipping out, so placing them in front of you will be the way to go.
If you are concerned about your 3-year-old being in their own seat, that's totally understandable. But in most cases it can be a little iffy trying to juggle a toddler in your lap while trying to paddle.
Don't worry that one of my recommendations is from the brand Ocean Kayak. Both of these kayaks would do great on flat water, such as lakes, harbors, etc...
With the kiddo in mind, also look at this article on kayak safety.
Can't wait to hear about your adventures on the water!