Two tiny old iPhones to use as cameras for kids

Your phones will not take esims
You only need wifi for Whatsapp, but if you want it for them to have access to you if lost and on the street then you use a sim card.
Often streaming like Netflix or Disney 'knows' where you are, so Netflix choices will change. Some don't work in all countries. But I download Netflix movies before leaving home and I can watch them when and where I want...even on the plane with no wifi.
As to wiping the phone clean, then you may want to hire the neighbors' kid to help with that...or Geek Squad or the iStore.
I use Android and my phones have had a slot for a micro data card. That would givebuourboldnphone more storage for photos.
You may need help for it, but if you can set your camera photo size to small resolution, then each one won't take up too much space...meaning you can get more photos in your phone memory limitations.
All this from a gran who only learns enough to make my tools work.

I agree with SoCalTraveler about resetting the phones. And when you reset it, make sure you use the Screen Time app, which will give you control over their phones. The 4s won't be able to use it as it was released with IOS 12 but you should be able to on the SE. This means that can't download any apps or change the passcode without your permission. Plus you can monitor their screen activity.
We have it set up on my 12 year old grandson's phone.

Your phones are too old for eSIMs but they could use WhatsApp or FaceTime to call you if needed. And you can use them without wifi - it will just take additional data. I call my sister and my daughter on FT when I'm in Europe.

The 9 year old probably already knows how to do this, and if not, will figure it all out in about 10 minutes lol.

I can't tell from your post if these are phones that have been living in a drawer, or ones that you are currently using. If currently using as your phones, then do not hand them to the kids. This way lies danger.

If they have been in a drawer, you probably already transferred the information to your current phone? So you can wipe the old ones. If you aren't sure, back them up to iCloud or Google or even your desktop/laptop, then wipe them. They should be fine to use as a camera, although you may need to set up Apple accounts for each one - not sure about that so I would second the advice to take them to an Apple Store or your techie neighbor of preference...

Rebecca is right - you will need to set up an Apple account for each of them, but it can be a child's account with restrictions. You don't want them using your Apple account as they will have access to some of your information.

The 9 year old probably already knows how to do this, and if not, will figure it all out in about 10 minutes

So very true. What about one of the new Polaroid cameras?

https://www.amazon.com/Polaroid-Camera/s?k=Polaroid+Camera

Please remember that iphones are subject to being stolen. One of our guides on a recent trip to South America said that he even keeps the windows rolled up to prevent people from taking them our a passenger's hands when stopped at a stop light. Thieves like phones just sitting on a table while you are eating. Minimal personal data on the phone!

Once you have set them up for use by the kids, buy those neck pouches with see through windows so they can use them with the lanyard around their necks when you are all out on the streets etc.
Make it a rule: No lanyard use, no phone.
That way they won’t forget them anywhere…..hopefully…..!

Wow, that was fast! Thank you all! This is such helpful information.

OK, so no eSims.

I will reset the phones.

Yes, they will also have their iPads, but not when we are walking around. I assume they already have their own Apple accounts, but I'll ask.

The nine-year-old does have a camera already, but my old phones are so nice and pocket-size, plus if they get lost or broken, no big deal. I'd be surprised if pickpockets would want these ancient models, but we will be careful on principle. And will look into the lanyard idea!

The phones have been living in a shoebox in their retirement --- I love my new phone, but do miss the small size of the old ones.

Good idea about the lower resolution. They both already make videos with their parents' phones.

Thanks again!

Nancy, it's easy to change the resolution. Just go to your settings, click on Photos, then look for the phrase "Optimize iPhone Storage" and click that. That will ensure that photos taken on the phone will be smaller with a low resolution.

Note that as long as they are saved to the Cloud, they can then download the full resolution photos once they get home from the trip.