Help with lighting equip for outdoor family shoots!

I've recently started doing some outdoor and around town family shoots. I'm using a 5dc and a 580exII for some fill. I want to take my lighting to the next level. I am working towards wedding photography even though this type of shooting is a bit different, I prefer to spend so that I can use the same equipment down the road. I'm thinking about a reflector kit, but I don't have an assistant. Do the stands work well with the reflectors? Then I started thinking maybe a second 580 or 430 with an umbrella and stand? My goals are to take my lighting to the next level above just available light and some on camera fill, and being somewhat easily portable so I can move around a park or beach rather easily. I don't have a decent tripod, so that may be an expense too. As for budget, I'd say I'm flexible but am saving for a
mark2/3 so every little bit helps. I prefer to spend a little more up front and buy once. Again, I'm hoping I can use some if not all of it in weddings. Thanks in advance for the help and ideas.

Ok, so after consulting with a friend, it looks like a good way for me to go is by adding another 580exII to the one I have, and putting it on a stand with a soft box. I am still not sure if I should get pocket wizards, or another flash activator. Can someone help me choose a good portable softbox and stand for a 580? I would like to order one soon, and am torn on whether or not I should just use my current 580 as a slave, or get the wizards.....

Noticed that you have not had much response.

I used to use my 580 off camera like you are suggesting but after some reading I heard that they are not powerful enough for a large softbox. You will probably be limited to a small softbox, in which case you may as well save some money and get an umbrella instead.

Dont forget to get some sand bags if you dont have an assistant to hold down the umbrella. I have had an umbrella blow over before and I was lucky that the olny damage was to the umbrella.

Unless there is very little wind unbrellas, etc are hard to use with speedlites, even with some extra weight on the stand.

I have had several speedlites on stands blow over with not too much wind.

I generally just use the speedlite on the stand and another on the camera, or just the off camera light.

Remember the soft gradation from shadow to highlight depend on the relative size of the light and the subject. Soft transitions require the light source to be larger than the subject so the light wraps and is muli-directional hitting the subject.

Just don't expect the speedlite to be the main light. Use it for fill.

Thanks guys, I ended up getting a second 580 exII and a small softbox and stand. I still need to mess around with them more, but am thinking it may be best to use just the speedlight on a stand instead of a softbox. I will start working with it as a fill light and see what works. I bought a book on lighting, so I have a bunch to learn. I really like what reflectors do, but don't have an assistant, so time for some experimentation....Tha​nks for all the advice and help.....