Would you let your 18 month old choose to potty train?

My 18 month old woke me this morning and says he needs to go potty (keep in mind he's never done this!) his 3 year old brother has been going on the potty since 18 months old it just didn't occur to me that my baby would be the same way his older brother was! My 3 year old still wears diapers during the night and nap time, but my method has always been all or nothing, diapers or no diapers except during nap time and nighttime, but I am 23 weeks pregnant and don't know if I am ready for that method right now even though it does work for my kids (they don't like their undies wet or dirty!) any suggestions? Do you think I could put a diaper on him but tell him "try not to get them wet"??