You might find this thread (where someone posed the same question) helpful.
I think that a variety of fresh, seasonal fruit toppings would be nice (eg. raspberry coulis), as well as some sour cream.
If you want a soup, perhaps a cold cherry soup?
You could serve some smoked fish and dark breads. I have served a ratatouille or other mixed vegetable casseroles that one could add some white beans for more substance. If you don't serve a mixed vegetable casserole, you could serve a hot or cold vegetable soup. A fruit salad sounds great for dessert. You could also serve some simple vegetable salads like cucumber or shredded carrot salads.
I haven't heard much about cheese blintzes, but they do sound yummy.
What about a 3 mushroom soup or tomato? I think fruit salad sound perfect.
A nice topping for your cheese blitzes could be a pesto based drizzle, or perhaps a zucchini and tomato saute with basil?
Would you tell me are you baking the blintzes? I'd love your recipe.
I sometimes blend high quality fruit preserves with sour cream as a topping for blintzes using a ratio that's greater on the preserves side than the sour cream side. Caramel sauce works with some cheeses also.
A fruit compote and a quality medium bodied red or white wine.
I wouldn't serve soup, except perhaps for a gazpacho or vichyssoise, with cheese blintzes. Depends on the variety of cheese and the topping. Neither gazpacho nor vichyssoise would pair well with fruit based toppings and fruit compote.