There are all kinds of delicious GF vegan desserts. If you don't want to take on a whole new set of ingredients, consider buying. There should be a good vegan bakery near you.

You can make all kinds of frozen treats from fruit. Sorbets, granitas, etc.

There are many GF vegan brownie recipes on the 'net, but I haven't made them in forever, so can't recommend a specific one. They don't require so many special ingredients.

I'm sure someone with more and better will post. I mostly want to say, yes you can, and good luck.

I tried several vegan brownie recipes and gave up not finding one that was decent. But I did find a delicious caramel cinnamon roll recipe :-)

I can’t help with the glutin free. However, I love the Philidelphia vegan creme cheese and Earth Balance vegan margarine. I also use Enjoy Life chocolate chips and Silk soy milk.

They can be substituted in any recipe that calls for the dairy versions.

If you want to keep the dessert a little more simple, you could make these cookies, some coconut cream whipped cream and some dairy free ice cream.

Use a flax egg in place of the egg called for in the recipe. And any neutral oil will work, you don't have to use coconut oil if you don't have any on hand.

Can they eat chocolate? How about chocolate truffles or one of those flourless/eggless chocolate cakes?

Ann Reardon has so many wonderful chocolate treats on her website, with step by step simple directions...

https://www.howtocookthat.net/public_html/chocolate-2/

I made Smitten Kitchen’s Chocolate Olive Oil cake recently and it was pretty good. If I were to make it again, I’d chill the baked cake until VERY cold, slice horizontally, and add a bit of good quality raspberry preserves as filling. Be careful if you do this because the egg- free cake is very tender. At least one reviewer has substituted GF flour successfully

I made my own glaze with melted chocolate, liquid espresso (made from instant worked fine) and olive oil.

Do serve with coco whipped cream substitute.

I have not used it, but King Arthur GF flour is said to be very good.

Be sure to check the ingredients on any gluten-free flour. Some of them contain milk powder.

Summer pudding could be made with GF bread. We serve with cream but I'm sure there are dairy free alternatives. Or a fruit salad made with tropical fruits.

I would ask the relative to supply the dessert. You are making the rest of the meal to go with their dietary needs, and they can bring something to share, so why not have it be the dessert? Otherwise, I would check in with some organic type stores (I found gluten/sugar free yums at a local store for my daughter's baby shower when she had gestational diabetes). Remember, you don't have to do EVERYTHING!

Kate, glad to see you posting! I've dealt with gluten-free baking for ages, but luckily never had to deal with dairy or egg-free baking. That really does narrow your options.... you might be able to substitute alternative ingredients, but I doubt if the end result is ever as good as the real/original thing. Everything good that I can think of involves butter or eggs or cream. :p

In my air fryer cookbook there's a recipe that they call churros..... They're basically choux pastry fingers, baked. Served with a vegan chocolate and non dairy milk sauce.... Can you make choux pastry with gluten free flour? They were very indulgent and delicious!

GF flour does make a fine choux pastry, but it requires butter and eggs, which are also not allowed in this case. eta, I see that churro dough uses oil and no eggs …. I doubt if it would work well with GF flour, but it would be easy enough to try an experiment.

There are a lot of chocolate mousse recipes on line which don't involve any of the banned items. But I've never tried one. I have attempted aqua faba meringue but it was not very successful.

What about baked apples or pears with a GF crumble stuffing (you could use GF granola), using vegan margarine? You could add plumped dried cranberries for a holiday twist. They could be made ready to bake and bake during the meal. There are really good dairy free frozen desserts available and Trader Joe's has a wonderful squirt canned whipped vegan topping that tastes exactly like whipped cream.

Here is one recipe: GF stuffed maple pecan baked pears

That pear looks really good. Lovely with seasonal spices. I'd still go with a French apple tart....or a tarte Tatin.