Disclaimer: I'm not a teacher. I do know a lot of them though.
@formerdxbteacher is the first teacher I've heard complain the workload is worse than England. I suspect it's subject/school specific but you don't hear of teachers leaving teaching in Dubai to go back to teaching in England for a better work-life balance! It's not the case that the workload is light or easy - ultimately a lot seems to be down to school/subject/individual. I did see someone recently say that they needed to get out of teaching because they were finding working 7.30 to 4pm too long hours and they were shocked that everyone else pointed out that standard outside of teaching in Dubai was 9-6 if lucky (i.e. longer) and without the holidays - note I'm not saying teachers only work school hours and don't do marking etc. This individual was specifically complaining that 7.30-4 was excessively long hours. I give this example not to say that @formerdxbteacher was only working 7.30-4 (it's pretty clear she wasn't!) but how subjective the concept of a high workload is.
I'm surprised class sizes above 20 is being brought up as a concern compared to England though - aren't class sizes normally closer to 30 for a secondary core subject (except maybe the bottom sets)? Even in Dubai my children's class sizes are more at the 25 level for core subjects at secondary. I agree that you're going to find class sizes are above 20. Same in primary, although you'll find having a TA as well is the norm (might be shared between classes in eg year 5/6).
In terms of jobs - plenty of teaching couples both work: for non-leadership it's not easy to survive off one teacher salary alone. That doesn't mean it's easy but it really depends on whether you personally want to work, or if you fancy taking a year or so off before starting. I say that because my reading of your post is that actually you do want to work, and you're immediately falling into a trailing spouse role where your husband has the big job and you are responsible for childcare etc. There's no problem with that if that's what you want but be conscious that it's very common for wives to move out here, decide they'll wait until the family settles to get a job, and then find themselves in a position where it's hard to find a job that justifies the impact to the family of them working. It happens in the UK as well of course, but if you currently both work why on earth wouldn't your starting point be you both work in Dubai! [Again - no issue if that's what you actually want, but this sounds like it's what will make your DH's life easier not what you want.] Personally I'd prefer to work and be able to have a helper at home to do the domestic work, and provide back up child care but this is very much each to their own. I like my job (most days).
What I'd do is apply and see what options you have. I don't know what subject/age group you teach but how easy it is to get a job varies massively - largely dependent on whether you teach a shortage subject (so similar to the UK) but also there are some subjects that are big subjects in the UK that aren't in Dubai (for example there is no RE taught in schools here). There's no point making a firm decision that you won't work until you know what work you could get.
Practically, is your husband's school an option? Very common for leadership to have spouses (usually wives because for some reason leadership is still overly male!) teaching at the same school - it's just convenient.
Another thing to be aware of (although there's not much you can do about this) is that if you decide you don't want to teach, either immediately or after teaching in Dubai for a while, options for teachers to get alternative employment at all are limited, and would normally involve a really material pay cut. I appreciate teachers face similar in the UK if they want to transition out, but a lot of the more basic starter office jobs (eg office administration) pay very very little in Dubai (way below UK minimum wage and long hours), and are employers are reluctant to take a chance on a career changer. You may find you it's hard to justify working at all outside of teaching if it would mean paying for childcare.
Final thing is that do be aware that education is one of the last bastions of the idea that 'if your spouse gets accommodation allowance then you don't]. You might be lucky that you and your DH both work in schools that don't apply this but it's the norm. I would therefore assume when looking at salaries that you don't get any accommodation aspect.