Don't feel bad. We decided to keep our three year old attending the childminder for 2 days a week throughout my maternity leave.
There were a couple of reasons for this,
a) he has always really enjoyed attending the childminder, has made friends of lots of kids this way and it's really his 'social life' I didn't want to suddenly take that away from him (and we wanted to keep his space with her open as he'll go there when I go back to work).
b) As I would be looking after a new baby I knew he'd suffer from the lack of time available to play with him (he'd been an only child for 3.5 years) I knew he'd adapt but I thought having 2 days where he doesn't have mummy saying, you'll have to wait until after I've fed the baby etc, would be good for him, and finally,
c) I wanted some 1:1 time with the new baby, I know I had 1:1 time constantly with DS1 and wanted to have at least some of that with DS2.
DS2 is now 15 weeks and I'm really glad we took that decision, DS1 doesn't always want to go to the childminder now that he knows I'm off, but I (sounds awful) love the 2 days he's away as it's two days I don't have to feel guilty if I can't play with him and can just focus on one child.
For the record, although I had a groin pain (and I wouldn't describe it in stronger terms than that) it wasn't a factor in deciding to send him to childcare, in the sense that I couldn't physically cope, we just decided it would be better for all of us if we took that route. I do sometimes feel guilty as I know DS1 would much rather be with me all the time, but I think about DS2 and that he needs some mummy-only time too, so that makes me feel better.