I did Elimination Communication with both my girls (4.5 & 2), wherein they don’t wear diapers at night. I created an environment for success regarding wetting the bed or getting up to take them. I agree it’s intense when you’re exhausted to have to help them too. And eventually, I imagine, they will take themselves…but that seems far away.
We have a sheep skin which repels water (pee) and a towel we put on top of that, so when it happens I take towel off, wipe pee off sheepskin and then put a new towel under the baby. I have found that there are still moments where accidents happen, especially if they are over tired. But most of the time, once they start to realize there’s nothing ‘catching’ the pee, they start to either sit up & wake, or call out for you.
Maybe letting your 3.5 yo know, you have to wake me when you have to go potty or having a small potty in the room for him to take himself might give him more empowerment. Saying we have to work together b/c mommy isn’t always able to get up might encourage him…just making suggestions.
And night weaning has been a bitch for us! I will be no help in making any thoughtful responses here. Best of luck! Many wishes of ease and happy sleeping.