They may come to nothing, but . . . . Acer seed needs a period of cold (a winter) for the seed to be triggered into germination. That process is called stratification. Collect up the fresh seed, keeping only the fat ones, and clean it off. Then dry it for no more than a couple of days. After that, soak it for a few days, changng the water regularly. This prevents fungal growth from forming. Dry the seed, and wrap it in paper towels. Close it up in a small plastic bag, and put it in the fridge for three months. If it starts to sprout in the fridge (and it does, sometimes) then sow it in a cold frame, being wary of late frosts. However, in the normal course of events you'll be sowing about mid Feb time. Sow it at about the same depth as the seed is thick/wide. Outdoors, in a prepared seed bed is fine. Stand back and wait. This is what I learned from growing trees for bonsai. What you are trying to do is as best as possible echo natural conditions, without squirrels, floods, pests, fungal attack, ants, etc. Phil