For environmental portraits a 14-24mm lens can work well but a go-to lens popular with many photographers is a 70-200mm, which can produce great perspective at the right focal length. When working with families, particularly when shooting a little more candidly, natural light works well but do pack essential lighting accessories such as a reflector. If you find you're out during the middle part of the day, particularly on a sunny day, find shade you can shoot in to produce a more even exposure.
Why this style of photography works is because, generally, people feel more relaxed out of a studio environment which will produce better photos. Throw a bit of fun into the mix and you'll soon have a collection of images that are unique and interesting.
Even if you know the people you are photographing it's still important to talk to them during the shoot as direction and encouragement will always be welcomed. Suggest poses and always get your 'money shots' in the bag early so you can have more fun and also shoot more candidly later on. Good shots to ensure you capture are images of the group as well as shots with tighter framing of individuals or one or two family members together. Direction doesn't have to come via your voice either. You could kick a ball into a particular good patch of light or ask children to play with toys in a certain part of the landscape you're working in. Remember that children do have a short attention span so make the posing part of the shoot as quick as possible then leave them to play, capturing candids with your camera as they do.
Backgrounds that contrast with what your subject is wearing can create vibrant images and don't get too hung up on having everyone in matching shades as a mix of colours adds interest and if they pick their own outfits, they'll be more comfortable.