We are five months in to placement, with a similar age child, and went out for 1.5 hours, very locally, after said child was asleep, with strict instructions to call if child were to so much as breathe funny. Attachment is improving every day, but it's fragile, and it is still very early days.
I really needed to get out, and it worked fine for us. So the benefits outweighed the risks of LO's distress, and setting us back attachment wise.
I think you will get different points of view, there are some birth parents who don't leave the baby for nearly 3 years, and some who dump with grandparents and go to Majorca for a week at 2 months old. Partly that's different parents, partly different babies. As adoptive parents, we've got a whole lot of attachment factors on top of that.
I think May is a while away. But I wouldn't be making any plans to go out and leave our LO for a whole evening in May. LO adores the grandparents, and they LO, but we're not ready for that.
Trust your instincts. I still feel our attachment is a thread, not the strong rope most toddlers have. It's been such hard work to get that thread there, I'm terrified of fraying it at all! If you're precious, so am I.