It's not knocking them over that is the worry. Toddlers use the stands to help them stand up.
Fill the stands with shot. Use spikes. Use something like clear silicone caulking to glue the speakers down. Silicone will peel off when you need to. The little anit-topple straps that come with all ikea stuff is great. You still will have to put a hole in the wall to anchor the strap from the stand to the wall.
Otherwise, buy klipsch cornwalls!
Fill the stands with shot. Use spikes. Use something like clear silicone caulking to glue the speakers down. Silicone will peel off when you need to. The little anit-topple straps that come with all ikea stuff is great. You still will have to put a hole in the wall to anchor the strap from the stand to the wall.
Otherwise, buy klipsch cornwalls!