You know your child best. if he is an easy going guy, and loves his grandma and his friends, maybe he'll make it. What if he does have a meltdown tho, will they be able to soothe him? Can you do a couple more overnight dry runs before May?
Even if you are not feeling letdowns, you probably are still producing quite a lot of milk, with around 5 nursings a day. Definitely bring a pump, better safe than sorry, believe me. Don't want leaks all over your dress, and a plugged duct to boot! Not feeling letdowns is quite common, despite good milk supply.
As far as the weaning issue, ideally that should be between you and ds. It is such a useful mothering tool. And it is so good for keeping him healthy. Not to mention, some toddlers are erratic eaters of table foods, and nursing fills in the gaps. And when they are sick, it keeps them hydrated and comforted and helps them get better quicker. Kids' immune systmes are not fully functional until age 6.
If you are confident and aware of EBF benefits, you will be able to express your wishes to dh. If you are ambivalent, he will keep pressing.
Yes, when you get back, after only 3 days, why wouldn't he still want to nurse, if you are willing? They don't forget how in 3 days!