I'm too late, but maybe could still help other people facing the same question.
I have both a Tascam DR-07 and a DR-03. Before these I used to tape with a Microtrack, and I was very happy to step down from a max sample rate of 96kHz to 48kHz in exchange for standard batteries and continuous recording past 2 GB. They don't have the best specs out there but the price is incredibly low and they've met my needs.
The DR-03, DR-08, and others that run on AAAs are incredibly small. I've gone through metal detectors with hidden recording gear before. Usually I get nervous about that but I can't imagine worrying if I'm carrying this recorder.
Initially I was worried about the combo power/hold switch. I thought maybe in one accidental movement I could bring the recorder off hold and shut it off in the middle of recording. There's a fair amount of resistance though, so accidentally sliding the switch seems unlikely. Also if will not shut off by sliding to the power position if it is currently recording. So I would have to accidentally slide it off hold, accidentally stop recording, and then accidentally slide it to power off. In the end this is no worse than any recorder with a dedicated hold button, and is actually preferable to any recorder that can be powered off while still in the middle of recording a file.
The input level control on the DR-03 seems better than the DR-07. First it is controlled by buttons rather than a dial, so using hold locks the levels, and second it seems to work like a preamp. The level control on the DR-07 acts more like an attenuator -- level 10 doesn't add any gain which is fine by me, but level 0 mutes the input and that seems risky, although I've yet to accidentally change the levels while using my DR-07.
Battery life seems good on all of them. No problem taping 3.5+ hours. I've heard complaints about the DR-08 battery life at the highest quality. I doubt it is coincidence that the DR-08 is the only one these basic Tascam recorders that records up to 96kHz instead of just 48kHz.
If I recall right, there are a few more specs published for the DR-07 than their smaller recorders, which makes me wonder if the smaller ones might not have quite as good specs as the DR-07. I think they're both good for a budget recorder.
Props to you for wanting to record your kids' school concerts. I wish I had more recordings of my own school concerts growing up -- good memories. When I have kids I'll definitely be taping their school bands.