June 21/22 is the longest day of the year. This is Midsummer, or the Summer Solstice. The word 'sostice' is from the Latin word slstitium, which translates to 'sun stands still'. On this day, the sun will appear to just hang in sky without moving. Litha is the day we celebrate the polarity between the land and the sky, the earth and the heavens. It is also a day find a balance between fire and water. In some 'Wiccan' Traditions, Litha is starts the battle between light (summer's Oak King) and dark (winter's Holly King).
For those with children, like me, Litha is a great day to celebrate outside. If you can go camping at the lake, this would be great. You could spend all day in the water and light a big bonfire at night. If this isn't possible, and you live in the city like I do, here's a suggestion. My family has this big outdoor 'firepit/fireplace' thingy. So, we spend the day in the backyard, playing in the sprinklers, or in the blow up kiddie pool, and then light a big fire in the firepit. It's big enough to have a decent size fire yet small enough to move to the middle of the yard so we can dance around it. That's the other thing about my family, they have speakers running from the stereo inside to the backyard so we always have music to dance to. I let my kids stay up late enough to watch the sun go down and then we sit around telling stories and having fun. Funny thing is, I'm the only pagan in my family, so when we're doing all of this, the rest of them have no idea that they are even celebrating the Solstice, unless of course I tell them, which I usually do. Luckily, my family is very open minded and are always interested to hear the reasons behind the things we do. And mostly, once I tell them that it's a certain Holy Day and whatnot, they actually try to remember the things I tell them. (Can you tell I love my family? LOL)