Hi Southern California Mom,
I'm not sure what your son enjoys doing, the number of guests or the budget you have for the occasion,so it is difficult to make specific recommendations. If you have a large budget and your son enjoys the amusement parks you could certainly plan on having your celebration at one of the parks. It will be memorable. The disadvantage here is people will go off to see the park, not be together as a family and community.
If your budget is more modest and/or you prefer to have more of a "celebration of your son" you could simply have a backyard cookout with all of your son's favorite foods. If you would like to provide a few more details we might be able to make more specific recommendations.
If you are opting for a "backyard cookout" type of event you might prepare a large display of photos, etc. of your son's first 17 years that tell a great story from birth to military. You could also have a cake/candle ceremony in which all of the guests light a candle while saying something great about your son and making a wish for him. If you do this, video it and take lots of photos.
Rather than have each of your guests send or bring a card, you could have them bring a sign (printed on 8.5 by 11 matte paper) expressing their congratulations, wish or thanks for your son. You could take photos of the guests holding their sign, presenting it to your son, and your son holding it. You could make a nice album that you and he can refer to while he is away.
You could also do a "mural" for your son. Mount a large (say 4 by 8 feet) sheet of foam core, heavy paper, or similar material on the wall about three feet off the ground (landscape arrangement). Have your son stand in front of the center of this display and look straight forward. Provide each of the guests with a marker. The guests use their marker to write a message to your son. Take photos/videos as they do this. Take several pictures of the finished product. Post the photos online where you and your son can look at them. (You may decide to let your son see the display once you've taken the photos, or you might decide to hide the display and give him access to the photos after he deploys.)
Instead (or in addition) to the "mural" you could have the guests bring along a second set of signs with a "surprise" message for your son. You could repeat the sign activity as described above (with your son blindfolded). You could send him a surprise email every week with his picture and the picture of a guest presenting him with one of the signs for the first several months.
You might also have some music / dancing if your son enjoys music and dancing.
You might refer to my Birthday Suggestions
website for more information/details.
Please do let us know how we can be of further help.
Ronald G. Shapiro, Ph. D.Education by Entertainment