Hello K.
My daughter is older, but she too used a paci for just a little while. It's meant to sooth the baby, but then it becomes a bad habit. You son gets comfort from the paci and now his fingers. The trick of putting something on his fingers to keep them out of his mouth will not work. You are going to have to love him thru this. Whether you keep removing his fingers from his mouth and telling him to stop and giving him a kiss letting him know you love him but he needs to remove his fingers from his mouth. If he is trying to sleep keep checking him and removing them gently yourself. It is going to be hard and long but you will get through it. The paci that your little lady is using get rid of it now, so you do not have to deal with this later. Children adjust easy to change we adults do not. Be firm but loving, it's going to break your heart when they cry and want to be comforted by object, don't do it to them. You and you husband's love is more then comforting to them. These are feeling they are developing by looking for comfort in objects like a paci, blanket, teddy bear. When they start kindergarden these things can not go with them, but your loving spirit can and will and they will have high self esteem standing on there own two feet. I pray for the best for you and your beautiful family,
you're a good loving mom and you will do fine.