Sorry for the delayed reply @flamingo40
He will need to fill in the PLF, it is pretty straightforward. They might not ask to see it but it is good to have it printed off just in case, it saves faffing on his phone at passport control.
There are lots of yellow taxis ready at the airport, or if he feels confident enough they could book an Uber when they arrive as it's cheaper? When I've had people come to visit, often their hotel organises transfers for them for free or a good price?
The airport is really straightforward, there are 2 terminals but they are right next to eachother so there shouldn't be any confusion.
I'd imagine they will be staying around the old square, there are lots of places to eat but prices are traditionally higher, especially if you need an English speaking menu. But honestly if they walk around there is such a wide variety of restaurants, they will be able to find one with good prices depending what kind of food they want. Traditional Czech food is amazing in this cold weather, so I would recommend trying sivákova, or goulash. Beer here is also amazing and super cheap, it is traditional that half the glass is made up of the head though, so that is normal.
A few words of Czech will go a long way and will make his service experience much better. So hello, thank you, goodbye etc...the pronunciation is so hard but any attempt will be appreciated.
If they plan to use the metro, they can buy daily tickets, or tickets for one journey. It is done by time, so they can buy a ticket that will last for 30 minutes or a ticket that will last for 90 minutes. There is a difference in price of about 20p so I recommend always getting the 90 minute ticket in case they get lost and have to change metro line. They time stamp their ticket on their way in and that is it. After 90 minutes it expires. This is probably sounding a lot more complicated than it is.
I hope this helps, I will post some links to restaurants once I have time to think a bit more. We are isolating just now with covid and my 2 kids are driving me crazy!! 😂