I would highly recommend to plan either a bottle - even if it's water or juice - or binkies / pacifiers for the baby. If you don't use either, definitely a sippy cup, but I would suggest the kind with a straw top. You may have to get them used to the cup now. The idea is to get them sucking and swallowing on the way up and the way down. When we fly with dd starting at age 6 mos to 5 years, we count to ten and have her take a sip, then count again. If you feel your ears popping, count to five. Once you're leveled off they should be okay.
We've also used dimetapp, and I would again but it's controversial lately. Like PP said, check with pediatrician. I haven't seen the earplanes, but I'm going to look into them (DH needs them more - lol!)
If you get up in the air and their ears are blocked (crying, etc), don't panic. Ask the steward / stewardesses for the cup trick. Apparently it involves a coffee / styrofoam cup, put a folded paper towel in the bottom with just enough hot water to wet it and put the cup over the child's ear, hold tight. One on each ear (looks rather silly, princess leia - ish) is supposed to help even out the pressure, moist air helps open up the ear canals? Most flight crews have at least one attendant who knows the trick.
Good luck!