Laura,
Since you have not had experience with camera flashes other than the built in flash, and do not have experience with strobe or off camera flash use, you may want to resort to constant lighting as you originally were going to try. That would be simple and would be a direct approach. If you do use constant lighting, and you are doing family size portraits, you will need light to disperse over the size of your group. If you wanted to try the stand I mentioned in my earlier post, and two 400 watt softbox continuous lights for example, that may work well for you giving you enough light and full control of it by positioning it as needed. Other methods may work, but to be simple and easily understand what you are doing per your experience level, the two 400 watt softbox continuous lights or two 400 watt shoot through umbrella continuous lights may take care of your needs by providing you with enough light. The softboxes will give you more control over the light output (direction/scope) than the shoot through (white) umbrellas but umbrellas will sometimes cover more area (spread it out more). I am not exclusively recommending this product, but to give you an idea of what I am referring to as an item, the following is an example of a set of two 400 watt continuous light softboxes in a kit.
https://www.amazon.com/gp/product/B009F37I8K/ref=pd_day0_421_23?ie=UTF8&pd_r...886XJ40JX0B3WH
I have continuous lights and flashes, they can be used in different situations alone or combined, so if you learn more about flashes later, you can utilize them with any continuous lighting you may purchase now. So, as I mentioned, two 400 watt continuous lights (with stands), a backdrop holder like the one I mentioned in my previous post, some cloth from the local Wal-Mart fabric center, and some hand clamps to hold the cloth on the backdrop holder may be a convenient set up for you per your present situation.