I make idlis the old-fashioned way - soak rice & lentils overnight, grind, let them ferment for 2 days, and finally steam them in special idli plates. The instant idli mixed available in asian/Indian grocery stores are almost as good and I use them occasionally too.
You don't need special devices to steam either. The batter can be steamed as one big pancake in any steamer or can even be cooked as a thin savory pancake. My mother-in-law bought me idli plates that make tiny idlis for little hands to hold. Iam trying to teach the twins to take bites (vs. shoving small pieces in which they have been doing so far when feeding themselves)
I fortify their idlis with thawed food cubes and almond meal. Idlis are one of the savory snacks Iam trying to get the kids to eat. My daughter will not take a second helping of them - she will only eat what I first put in front of her. Iam trying to figure out if it is the temperature that is bothering her. My son is OK with them.
Plain idlis are usually seasoned with a little salt and nothing else. So they are eaten with chutneys and Indian pickles. For now, the twins do not get any chutney but my mother-in-law slathers some honey on the idlis sometimes.