I FIREd on 30 September, 2013. Our daughters were 9 and 7 at the time. I still do some very part time consulting because I find it interesting but am home more days than not. DW has been working part time for several years now (after deciding that being a SAHM wasn't her thing).
The kids were used to usually having DW around when they got home from school so having me around didn't raise any questions. Since we are both seen to still be working at least some of the time, it hasn't been an issue. If/when it comes up, we will tell them we were lucky enough to save a bit when we were working full time so we could spend more time with them.
I'm back at university doing another degree (part time) and DW (aka tiger mummy) "encourages" me to study in front of the kids and has been comparing their grades with mine.
We haven't had any issues with friends/neighbours. If asked, we simply tell them we work part time so we can spend more time with the children. A few of those who know I've retired ask what I do all day and whether I am bored, but that's another issue.
I think it helps that DW and I both keep ourselves pretty busy - the kids don't see us lounging around watching TV or on the internet all day.