Hi R.,
Definitely, do not put him in pull-ups! Pull-ups are expensive and prolong the situation.
If he is telling you that he does not want to wear a diaper at bedtime then I think you need to honor and respect his wants/needs. This is a milestone-
The same routine applys at bedtime as at nap time. Take him to the potty before bed and then tell him that if he needs to go to the potty during the night to get up and go or to get you for help! That's what we did and it worked.
Also, just know there will be accidents until he gets the hang of it, so have plenty of clean sheets ready to go at his bedside so you do not have to look for sheets at 4:00AM-
My two girlfriends also took this approach and it worked-yes we were changing sheets at 3:00/4:00AM but not for long and in the long run its so much better than wearing pull-ups, which are simply a crutch!
Also, I have another friend who just told me that her almost 6 year old still wears pull-ups-I do not recommend this path.
Good Luck and once he can use the potty himself and hold it until the morning you will be soooo happy yes it will take time and some effort but well worth it and will not break the bank!