The free and easy-to-use benefits calculator at Turn2us.org.uk can help you work out your entitlements.
The calculator includes a 'better-off' tool so that you can compare your situation now to your situation if you were to stop work or reduce your hours.
However, it is quite likely that your income may be too high to qualify for means-tested benefits (such as tax credits or Housing Benefit) even after you leave work.
If you have not already done so, your wife should check with her employer what entitlement she would have to contractual maternity pay if she goes on maternity leave. Otherwise she would have to claim statutory maternity pay.
You can claim Child Benefit for your second child and Child Tax Credit if your income is low enough.
You may have already thought of this but you should work out how much you would have left to live on as a household if you were to leave work, once all the bills are paid, and whether there are any ways to reduce some of your bills (for example, by switching energy suppliers).
David Samson is a welfare specialist at Turn2us