Without thinking deeply (so perhaps I should not be posting this), the first thing that comes to mind is to put the photos on an SD memory card.

Buy Apple's SD card reader adapter. Plug it into the iPad, import the photos.

I only buy MicroSD memory cards now, so I can use them in multiple ways. There are compact USB adapters for MicroSD (I use the tiny elago Mobile Nano II USB 2.0 microSDHC Flash Memory Card Reader) so copying from the old computer is straightforward.

Many MicroSD cards come with an included full size SD adapter for the MicroSD card, so plugging it into the Apple adapter for the iPad is also straightforward.

I have ordered the new SanDisc 128GB MicroSD card. Expensive, but when you need the space, you need the space