My situation was quite different although has some similarities - I never planned to be a SAHM, but was offered and took voluntary redundancy when on second maternity leave - I had been intending to look for a new job when I returned to work and cost of childcare outweighed my take-home salary at the time, so it seemed to make sense.
So, I took redundancy and thought well I might as well enjoy some time with the DCs and spend a little time planning next career move and then get next job… But then we moved across the country to somewhere where DP now works away Mon-Fri and I didn't know anyone, and suddenly felt much more reluctant to look for work in this situation.
We had planned to have third DC with a similarly short gap as between DC1 and DC2 (c2years), but have ended up with a much longer gap because of the stress of moving and various things. Result is that I am now pg with DC3, and by the time this one is born and I am ready to look for a job again I will have been out of full-time work for at least 7 years - much MUCH longer than I ever would have imagined.
(And I still have very little clue what to do when I do go back)
Anyway, your situation - I think before you decide whether or not to ttc no2 you should really think about how you feel about SAHMing and about your work and career.
Ime being a SAHM to a baby and toddler was v different to being on mat leave with just one - the latter was tough, but full of other people also off work and with time to talk and have coffee etc. You can't do so much baby stuff when there's an older child around, it can be harder to make new friends, and if you're friends from DC1's mat leave are back at work it can be much lonelier.
Also, consider that it's going to be much easier in most professions to get a FT job then apply for PT working after Mat leave than to get PT working from the get-go. May not apply to you, but if it does and you do want to work PT, it might be more sensible to try to get a new FT position, wait til you qualify for ML, have DC2 then apply for PT working on return.
Do your work offer any kind of career counselling/coaching as part of the redundancy package? If so I would definitely take it up and explore your assumptions and expectations about work, and think through what your options are carefully, and if not perhaps consider trying to source something similar privately and get your thoughts straight before you fall into making some pretty major life decisions that you could end up feeling unhappy with.