You certainly can. Although irrigation hose may not be code, it sounds like it doesn't matter for your application.

Be mindful though, anytime you put conduit or pipe underground it will fill with standing water over time (condensation or if a hole accidentally gets created). In situations like this where the cable may be potentially submerged (even in a conduit like housing), I would recommend a filled cable like this one:

Gel filled Cat5e direct burial waterproof cable

Your cameras run at 10/100Mb/s so a Cat6 cable would be overkill unless you are going to be running 10Gb/s cameras anytime soon. CAT5e is rated for 1Gb/s up to 330ft., so there is some future proofing in your case.

TruCable did a nice little blogpost about gel filled CAT cable and they even have a little walk through of how to work with gel filled cable. The difference with gel filled is adding the step to clean the gel off the wires so you can terminate them.

You can find that post here

Either way you are on the right track. If you want to use the irrigation hose, I would use filled cable in the hose as a precaution in case water does start to gather in the hose.