First thing to do is narrow down exactly what you need and what competencies you need.
Is level of English important to you?
Do you need a driver?
How long do you want them to stay?
If you're looking for them to help you with general care of your tiny babies then you certainly want someone with newborn care experience.
How many hours do you want them to work each day?
Are you planning to self-recruit or use an agency?
I feel you're vey borderline for having an au pair and may be better off looking for a mother's help or newly qualified nanny who should be able to help with both your DS and the twins competently for all they may need a bit of additional guidance. They'll also do nursery duties for you (and we all know how much laundry just ONE baby generates). Many NQ nannies will bite your arm off for the chance to work with newborn twins too. Alternatively you are looking at someone who is an early years/childhood professional or nurse or similar in their own country.
Your other option, if you want a lot of support in the first few weeks is to separate out the role into au pair and post-natal doula, which could work out more effective than a nanny as you're buying in general help plus specialised help (for a short period).
The following employment/recruitment stuff applies to both au pairs (who are legally the same as nannies but shouldn't be expected to do the same job) and nannies:
- Write your advert very carefully, be clear about what you want
- Have a checklist so when you receive applications you just go down the list include things like nationality (EU citizens can do anything except Romanians/Bulgarians where special rules may apply, Aussies, Kiwis, Canadians and Japanese may be able to do anything depending on their visa, anyone else is a non-starter unless they hold dual passports or have ILR), driver status, previous experience, having lived away from home etc.
- Bin any applications that don't meet your requirements no matter how 'nice' they seem
- Depending on how you're recruiting correspond by e-mail/set up a phone interview where you can describe the role in more detail and ask a few questions about them
- If you like them after that then set up a face to face interview, even if you're using an au pair and you need to fly them in to stay for a weekend - you are going to be a vulnerable, hormonal mess recovering from major surgery so you need to have met the person, had them around overnight and imagined living with them before you commit
- When you're ready to make an offer make sure they're clear on their hours and their pay. If you're paying over £100 a week make sure you're clear on your responsibilities as an employer regarding PAYE
- Send them a contract, there is a lot of guidance on here about creating one, and a copy of your house rules, again lots of guidance on threads on here, so they can see it all in writing, especially if their first language is not English
-When they arrive make them feel as at home as possible, don't throw them straight into work. Take the time to show them around the local area is vital - for this you may want to consider your start time very carefully as you probably don't want to be dealing with all this 37 weeks pregnant with twins (BTW don't expect the au pair to look after your DS while you're in hospital all the time, that's not fair, although a nanny would be perfectly capable).
- Be prepared to have a week of the au pair shadowing you and asking a million questions. Write down as much as you can in a manual (how to work the washing machine, step by step instructions for 5 simple family meals, which brands of household goods you buy so they don't get confused when you ask them to go to Tesco for milk and there are 40 different choices)
- Show, and have written down, how you want your babies cared for ESPECIALLY if they are going to be making up formula feeds (print off the DOH guidance and explain it with reasons) or bathing them (some countries go overboard on skincare products, you may not want this) - don't assume anything.
- Keep the channels of communication open. If necessary explain that you will be feeling vey sensitive and delegate management to your DH/P. That way you can write down things which are troubling you and hand him the list to discuss with the au pair without fearing you'll burst into tears because they've done something wrong.
I can't stress enough the need to have clear and realistic expectations. It is considerably better to underestimate than over-estimate.
Good luck!