Term Time Only Contracts advice ref charges greatly appreciated?

[soberton]

Hi
I am a childminder in the South of England and have had a call from a school teacher looking for childcare for her two children two days per week. Their ages are 3 and 1 and would be looking for cover 1.5 hours before school, take the DS1 to pre-school, collect @ lunchtime and look after him until teatime collection on one day, meanwhile I would have the DS2 with me all day. On the second day both children would be with me all day together (about 10 hours approx). The parents would like me to provide breakfast and lunch for both children (which I am happy to do, but as I haven't had young children with me for a while - my present ones are all school age) I wondered if it is reasonable to charge extra to cover these meals (although my hourly rate, currently £3.50 includes drinks, healthly snacks fruit etc). The local price of a school dinner is £2 per day from Sept.
Also do you charge whilst the older one is in pre-school, it is local to me and I would be a point of contact for them if needed, whilst parents are at work.
Also, how many of you charge retainers during the holidays for teachers children (EYFS age groups) when they don't require cover?
Hope this makes sense.
TIA

I don't charge extra for meals (I have to feed DD anyway and put down a set amount on my expenses sheet for the mindees meals) but it is perfectly reasonable to do so if you wish.

I would charge for the older one being in pre-school - you can't offer those hours to anyone else so they're effectively taking up a full time space,

I don't charge a retainer for school holidays but I wish I did - it's a real struggle in the holidays without the money coming in from my full-timer.