First of all, please accept my sympathies for your loss of a loved one, but also my admiration for your strength as a military wife!
I took my daughter on her first airplane trip when she was 5 months old (just the two of us!), and it was great. One thing I would suggest is a dose of baby sudafed about 10 minutes before takeoff. It helps to relieve the ear-nose-throat congestion that intensifies ear pain. It was actually a flight attendant that got me to try it for myself (the regular kind) years ago, and I've never flown without it since.
I also encourage you to take advantage of the 50% discount most airlines offer and get that baby his own seat. Otherwise, if he gets fidgety, you're stuck wrestling him with no alternative. Also, it gives you a little buffer between yourself and other passengers (you won't be closely sandwiched by unsympathetic strangers on both sides). And when all those other fabulous MamaSource suggestions finally get your precious son to fall asleep, you can set him down and enjoy a good book (or well-deserved nap) for yourself! In fact, I found it incredibly cozy to rest my head on the side of my daughter's car seat and enjoy her soft snores till we landed. Just make sure you streamline all of your other carry-on items, or you'll find yourself clunking every other passenger in the head as you try to carry the babyseat down the aisle!
Just one other note of encouragement--my brother was afraid to take his first child on any long trips at that age, certain that confining a baby for that long would slow his progress in crawling/standing/walking. Now that he's the proud (and overworked) father of FOUR kids, he's sorry he missed his chance. Let me tell you, I took my daughter on many long trips in those first couple of years, and every--yes, EVERY--major milestone of development happened IMMEDIATELY afterwards! It's as if each experience flicked on another lightswitch in her brain! And with every landing, I could hear the relief as other passengers complimented me on having such a good little travel partner. Congratulations on having the spunk to give this a try--in spite of the sad circumstances, your loved ones will enjoy this reminder of fresh, new life, and you'll always treasure these memories!