Separate networks - same internet connection

So my question is whether it is possible to create two separate networks were the second airport express repeats the internet connection from the first airport express but on a different wifi network in order to ensure that not too many devices connect to the same airport express

Yes, if the second AirPort Express connects back to an Ethernet port at the head end of the network.

No, if the second Airport Express wirelessly extends the network from the fist Express.

The current version of the AirPort Express will support up to 50 users, so if your single Express produces a signal range that is acceptable, it's possible that a new Express would be all that you need. Although the specifications for the current Express say that it will handle 50 users, realistically things start to get slower and congested at about 25-30 users.

If you buy from Apple, you do have a 14 day return privilege, so if the new Express does not work out, you return it for exchange or refund.

As we already explained, you need another router......like the newer version of the AirPort Express or something from another manufacturer.....that will support 25-30 devices easily.

Meant to add that if a single newer version of the AirPort Express will not provide the signal coverage and range that you need, then you really will need two newer Express devices to do what you want.

Using a newer Express as your "main" router and an older version that will only support up to 10 wireless clients might work, if there are only 4-5 wireless devices near the old Express. Much better to use two newer versions of the Express though.

Good luck with your "solution". I do not think it will work because your AirPorts will not easily support the number of devices that you want to connect to the network. If it does work, that is great.

I have had the same issue as you in the past.....the solution that works is to have an AirPort router that is capable of generating far more IP addresses that you will ever need. That way you don't run out of IP addresses, and the conflicts do not occur.....since you have a much larger bank of IP addresses to use.