Oh and when they ask if you have any questions, don't say NO. Have a couple of prepared ideas in your mind, and not about holidays/pay etc. Perhaps in your case about training courses you could go on to supplement your skills, or gain proper qualifications to be able to offer them more. That is if the subject has not been covered already.
Think prior to the interview what you can offer, which the other candidate MAY not be able to.
Your mothering skills are VITAL here, you can use it to your advantage. You have already shown commitment to caring for people, you are used to multi-tasking, keeping calm, working with troublesome toddlers (and old people often have similar slightly selfish needs). Bear in mind being a mum uses an amazing amount of different skills, everything from multi-tasking to careing as already said, but negotiation (I was always told the best negotiators are little kids!!) Organisation, time keeping (school runs etc) Also the albility to smile when cleaning up poo and vomit (!) and not being afraid to work hard and get your hands dirty.
How local do you live? This can be a real advantage if you only need walk to work (no public transport excuses)
How flexible can you be? At the moment the job maybe for set hours etc, but there maybe opportunity to be flexible as your circumstances change
Have you ever done work like this job? even if it was years and years ago it is worth mentioning. If not think of what skills the job entails, and match them to what you HAVe been doing (eg Motherhood)
You are SOOOOOO qualified for this job, words on a bit of paper are not important, practical experience is.
If I were an emplyer I would usually look to employ a mother as they make the best, most loyal, most flexible, commited workers in the world and they are not too hung up on the whole ego trip (usually)
Good luck