An excellent station to snap away at is Atherstone, easily accessible by rail from Tamworth with an hourly service (xx:47 for most of the day, trains come back at xx:23 for most of the day) and only a short ride on a 350 away. Annoyingly I've not uploaded my photos from my day out including a trip to Atherstone yet, however I'll return and edit this post with an example of what you can get there.
Be forewarned though, the footbridge has been out of use for quite a while for replacement works. December 2009 the work apparently started, but it's a long way from completion! So it takes a couple of minutes to use the alternative route to change platforms.
If you're willing to go a bit further north, Kidsgrove is also pretty good for photography. Again, an example of what you can get there will follow soon. Alsager's quite a nice station to get photos at, also un-manned. Not terribly busy though with just an hourly EMT service from Crewe to Derby and vice-versa and an hourly London Midland Crewe to London and vice-versa service, operated by EMT 153s and LM 350s.
As for Crewe, there's some decent opportunities there, most of which that come to mind are at the north end of the station shooting stuff coming from the north. Don't forget though that the vast majority of the freight uses the dive-under to the north of Crewe which re-surfaces to the west of Crewe station, so you won't get to see much of that. Stafford is far, far superior for that as everything has to pass through the station.
Rugeley, never been there for a photography session although I'm keen to try it. Lichfield, again not been there for long before but it looks limited for opportunities. Tamworth is good in my book, as is Nuneaton. Water Orton, a good place to go for shots but I prefer to go to the footbridge a very short distance east of the station for photography. I didn't see much freight when I went there, but different days mean different levels of freight at different times, so do some research if freight traffic is important to you.
Doncaster, not been there for years but I seem to recall it wasn't bad for photography last time I went there. None of the stations mentioned in this post will give you any problems, so long as your grandchild and yourself behave sensibly.
Welcome back to the hobby and enjoy your trip/trips out
EDIT: Some of the photos I was going to link to this morning follow.
Kidsgrove, with a southbound 390
Longport, with a southbound 323
Tamworth Low Level, with a southbound DRS working
Atherstone, northbound 70004
Atherstone, northbound 390
Atherstone, southbound 379s on test
Lichfield Trent Valley, with a northbound 350 seen from the stairs to the High Level station (it's my best and almost only shot from Lichfield I've got online)
Hope this helps!