Benadryl's a good idea for kids with colds as it will make them feel better and make them sleepy (not a bad thing on a plane!). Haven't tried the earplanes, but a 4 year-old could possibly be talked into wearing them if you tell him it will make his ears feel better, etc. Then the 2 year old might want to wear them because the 4 year old is. Good luck - it's always a crap shoot when taking kids on a plane!

If the colds include significant congestion - DO NOT FLY. You can damage your ears.

Here's more info, but Googling will get you a variety of perspectives:

http://tinyurl.com/4la32w

Last winter, I flew with a pretty bad head cold, and even with antihistamines, I could not decompress for the life of me. I was partially deaf for most of the following day. This had never happened before. My son had been coming off a cold, and I guess he still had fluid in his ears, because he screamed bloody murder during ascent and descent (descent is more dangerous to your inner ear if you can't decompress).

I always have severe problems with my ears on airplanes and have been to many doctors, including several ear doctors, an allergist, and two family doctors. I have officially been diagnosed with Airplane Ear. I've been told my ear tubes are perpetually swollen from an unknown allergy. Here is what I do on a plane as an adult (I don't recommend all of this for kids). First I take two prescription nose sprays daily, one is an antihistamine and one is a steroid. Then I start taking Sudafed 3 days before the flight. On the day of the flight I take a couple of squirts of Afrin in each nostril. Best to do this no less than 20 minutes before the plane starts to descend. (It is difficult to know in advance when that will be, but Afrin lasts 12 hours so take it earlier.) I have a supply of balloons on hand and if things get bad I hold my nose with my fingers and blow up the balloons. That really helps, but only if I've already taken the medicine. I keep a supply of life savers on hand to make sure I can continue to swallow. Also, I only fly very large airplanes and I make sure I only go up and down once -- only take non-stop, direct flights. Newer, better pressurized planes are better. If I have a cold, I don't get on a plane. I have been told that if my ears don't pop, I could burst an eardrum. The doctors, however, don't seem concerned about this. They say the excruciating pain will then stop and the ear will eventually heal itself. If none of this works, and that has happened without my eardurms popping, then I spend two weeks recuperating with weird noises in my ears and with hearing that sounds stuffy. Also, my balance feels weird. I've been told that this condition is caused by the breakage of blood vessels and my ears return to normal after the blood vessels heal. I tried the earplugs marketed to help this condition, but they made things worse. So, all in all, it is better not to fly. I would never take small children on a plane when they are congested. It's surprising how many doctors don't really know what to do for this. It took me going to several doctors and then checking back with each one to see if what another recommended would help. So, all of my doctors know about all of the medicines I take. I have tried everything, and this combination is the only one that works.