Outdoor Portraits with Nikon D90 amateur photography?

Doing a outdoor group and portrait photos for family members. I have been out to the park and looked at the location, and have found a couple of shade spots (as we're doing this around noon) that will be good, but still not at peace with my knowledge with taking portraits.

My question is, what mode other than Automatic or Portrait Mode and what settings (ISO, Aperture, Shutter) is just a safe place or range to stay in when doing outdoor portraits. I'm still very much an amateur so please keep that in mind, and still in the learning process about my Nikon D90.

Working with nikon d90 and 18-105mm lens that come with the camera, and the only other things I have is light reflectors(gold, silver, white) and a remote release, and a tripod.

Any help would be greatly appreciated.

I tend to use spot metering for portraits. Reflector is a great idea - will be handy to bounce a little light into shadow areas.

If you're not comfortable with Manual settings, then I suggest you use aperture priority (A) and set a wide aperture to get a shallow dof & for single portraits shoot around the 50mm-85mm focal length. For the group shots you'll have to go wider (18mm or so).

Keep the ISO as low as possible. In A mode, the camera will take care of the shutter speed.

You're more set than most people. Fir t off, DEFINITELY be shooting in the shade. Thank you for knowing that.

Secondly, use the reflectors for "fill light". This basically means you use it to fill in the shadows that happen under people's eyes, nose, etc. The nice thing is that using fill light does NOT affect your exposure. So get a good ballpark area for exposure before worrying about adding fill. Fill light for the group will be trickier; you may find yourself using multiple reflectors. For single shots, one reflector will be fine. You basically just have an assistant hold it and bounce the ambient light into their face from below. It's very easy to tell when it's working. I would use either white or silver. In the shade, using gold will add an odd warm cast to their face that doesn't mix well with the blueish light you will have everywhere else.

You'll want to be zoomed in all the way if you are going for a thin depth-of-field. Shoot in "A" mode, and select f/5.6 for your aperture. This is just for the single shots though. For the group shot, I would be zoomed out as far as you need to to squeeze everyone into the frame and shoot at about f/8.
For the single shots, this will put you quite far away from your subjects. For that reason, if you can get fast enough shutter speeds at ISO 100 or 200 (at least 1/160 of a second to avoid blur), I would stay off the tripod. Otherwise, use the tripod; it will limit your movement but help keep your pictures sharp.

You will not need the remote release.

Good luck! Just don't stress about it too much. You learn best by doing. If you enjoy portrait work, it would be a good idea to look into getting a 50mm f/1.8 lens. Awesome easy depth-of-field, good focal length, lots of light for fast shutter speeds, and very sharp glass. All for less than $150. Another accessory you might want to get is a Speedlight SB-600 with a miniature softbox diffuser. A little less than $300, and provides way easier fill flash than messing with reflectors.

Set your camera on AV (aperture priority) set your F-stop no higher then 11. ISO at 200. Use a tripod to reduce shaking if the light needs a longer shutter speed for exposure. Keep the lens at around 18-24mm. Physically move in to fill the frame.
Use your silver reflector to help reduce harsh shadows (you might not need it at noon in the shade, but if you do set your stand low to angle up, and adjust as needed to reduce shadows).
Oh, and have your flash on.