You can take along lunch, water, a small first aid kit, and a guidebook in the pack. Come midday when it's warm, just stuff that extra sweater inside. When it comes to larger, more expensive pieces of necessary equipment like tents, backpacks, and skis, a good way to find out what you prefer is to rent them for several outings. In the long run, you'll save money by purchasing the equipment that you want and will use. Keep in mind the end of the season is often the best time to buy all kinds of gear at economical prices.
People working in sporting goods stores are a wealth of information.
They can tell you how to use and care for the equipment you buy, and probably suggest favorite places to hike, bike, ski, or fish. Right from the beginning get everyone into the habit of taking care of the equipment both in the field and at home. Read the instructions. Make sure everyone knows how to use and care for things before the trip. When you get back, get the kids involved in clean-up oil, dust, wash, and dry everything before you put it away for the season.