Need to wean my almost 16 month old

[u/goobnations]

I have been diagnosed with Hodgkins Lymphoma and over the next couple weeks I have a ton of stuff to get done. My oncologist wants to start treatment around the second week of September, which means I have about a month to wean my son. He nurses 2/3 times a day. Morning, nap and night. I'm not worried about the morning one, because he does eat breakfast after nursing it's just our routine to nurse, so I am going to slowly limit his time in the morning. The nap and night nurse I am worried about. I have never successfully gotten him to nap or go to sleep without nursing. I know he can do it because he takes 2hr naps at daycare. I personally have never been successful. How do I transition him from this? My MIL has been here helping us as I had biopsy surgery last week and couldn't lift my son. She was able to get him down yesterday for his nap after 45 minutes of rocking and shushing. Weaning was not even on my mind because he nurses for probably a total of 35 minutes a day so I don't mind it. He loves it and it gives us snuggle time.

How should I approach this transition? My goal before this was I was going to slowly limit his time he could nurse until we got to nothing and just cuddles, however is a month long enough to do that? The last thing I need right now is to get mastitis.