For something that needs to be dirt-simple, I like the Cannon Vixia line of digital camcorders. You can get them with extended batteries and large-capacity memory cards and cover a 2-hour meeting without a break. They have a lot of automation in them which makes it harder to goof up. You’ll want to make sure you get one with an audio input jack, so the wireless lav can get in.
With wireless lavs, you kinda get what you pay for. Better performance (noise rejection, clarity of signal) and longer duration without stopping to change batteries in mid-speech costs more. Most wireless I’ve dealt with peters out of power at about an hour. I would not be surprised if the lav mic system costs more than the camera. Brands to look at include ElectroVoice, Sony, Samson. There’s good catalogs at B&H photo-video as well as Sweetwater sound, Markertek, and Fullcompass,
Think hard about the need for the mic to be wireless at all. If a lecturer is working from a lectern with notes, you may as well use an omni-directional stick mic mounted there, and reduce complexity and expense while increasing reliability. I never run wireless unless hardwire is for some reason impractical.