If the planes, engine and radios all sat for 3 years they should all be replaced. Send them to me and buy all new stuff!
-- You should be find with the exception of the batteries. I would not trust the old ones unless they still have a charge on them. When a multiple cell battery pack discharges lower than 1.1v per cell. (your packs are likely at 0v now) bad things start to happen and the pack can be damaged. It is not worth the risk. dump the packs and get new ones. Sounds like you did a good once over on the planes so you should be in good shape there.
Only thing I would caution you about is treat each plane like it is new (first flight) Be sure all the servos move the correct way (nothing got reversed over the 3 years) Strange things can happen in storage!
Good luck and welcome back!