This is a perfectly normal thing for a grandmother to get her grandson for Christmas, but his mom and I were early in the process of learning that our son would prefer Barbies and fashion accessories over footballs and trucks. We have the whole scene on video: Just as he tears the paper off of the toy, he flings it aside and exclaims, "Oh it's a truck," in the most "whatever" voice his 3-year-old self could muster. We laugh about it now, but at the time we were mortified to see him voice his disappointment so loudly. Ironically, the truck turned out to be one of his favorite gifts that year (it had lots of flashing lights and played techno music when you turned it on), but in the moment, the last thing that seemed fun to him was a toy truck.
We realized two things after this happened. First, we needed to do a better job of explaining gratitude and appreciation for any gift, regardless of how fun it might seem in the moment. After all, there are lots of kids who would've loved to get a toy truck (or any toy at all) for Christmas that year. These days all three of our kids are much better at this. They understand that some gifts can be exchanged, especially if it's a duplicate, but more importantly, that any gift is an expression of love. Besides, things that seem disappointing at first may end up being lots of fun once you start playing with them. We've used the example of the truck many times.
Second, we learned that we needed to figure out how to make our son's interests known to anyone who might be shopping for him. During those early years, this could be much tougher than you might realize, simply because most adults assume that every little boy would love to get a Transformer, or a Teenage Mutant Ninja Turtle. But our son didn't care about those things, and if someone is going through the trouble and expense to buy him a gift, it might as well be something he'll actually enjoy, right? Getting him a gift that's in line with his tastes (and not just a generic "toy for boys") shows that the gift-giver actually knows him and understands what kind of things he's interested in. It's the thought that counts, as they say, and surely that thought isn't, "Here's a gift you might not like. Oh well."
For some surely old-fashioned reason, many adults are uncomfortable buying dolls, princess accessories, or fairy costumes for boys. Though I recognize that it isn't exactly the norm, I'm baffled as to why you would assume that you have a better idea of what my son would want than he does. As soon as he was old enough to express his opinion, he always went after the "girl stuff." Ask him who his favorite Muppet was, and you'd hear Miss Piggy. Favorite Disney Character? Minnie Mouse. Backyardigan he sang along with the most? Tasha. He was always confident in his tastes, and without fail those tastes gravitated towards the girl characters and toys aimed at girls. Once his sister came along, he would light up as she opened her gifts, delighted at her pink clothes and mermaid toys. So sure, friends or family could get him some army men if they wanted, but they'd collect dust while he played with his Jessie from Toy Story doll.
But he always knew what he wanted, and we followed his lead and learned to be confident as well. If someone asks what to get him, we're going to tell them things he actually wants. I know if I were to give a child a gift only to learn later that I'd totally misjudged their interests and they never played with it, I'd be pretty disappointed in myself. So by the following Christmas, we were not shy about giving people gift ideas he'd actually like. And if for some reason people were still unable to bring themselves to buy a play dress for a boy, they could always get him art supplies. Our family is supportive and understanding, though, so thankfully we've never had any major issues. And these days... he's a big 8-year-old now... anyone interested in buying him a gift knows him well enough to not miss the mark by too much.
If you have a gender-creative son, especially one who's just coming into his own and figuring out what his interests are, it can invite some awkward conversations when people ask what's on their Christmas list. Our son got plenty of superheroes and sports toys in those early years, both from extended family and from us. But he never had much interest in them, and once it was clear that this was who our son was, we took the approach of being honest and upfront about it. Nine times out of 10, it's no big deal. We definitely worried at times what people were going to say when we told them the things he really wanted. But even your more conservative family members may surprise you, especially when you explain that they're free to go "off list" and get him a baseball mitt, but more than likely it'll be substituting for a wig to go along with the Tinkerbell costume he's also getting.
The thing we most want our kids to understand about getting gifts for Christmas is that it's done out of love and generosity. We want them to appreciate any gift, even if it's socks and underwear, and to express that appreciation loudly and repeatedly. They recognize how lucky they are, and how many people in the world are not as fortunate. But our part of the bargain is to be honest about them, and to not put other people in the position of unknowingly disappointing them. This way both the gift givers and the receivers can get the most out of the experience, and share the happiness of the season between them.