Women tend to undersell themselves so I wouldn't worry too much about your ability. You've proven yourself already. But it's a question of 4 things IME;
- Your own priorities
- leadership team backing/relationships
- The economic climate
- Opportunities for other senior roles.
1 and 2) are related to performance. If you've already been working at a higher level and built up strong stakeholder relationships its much easier to get going from day 1. But also, you'll need to be working much harder. I don't mean a strict 9-5 but the women I knew picked the kids up from nursery, did dinner, put them to bed then logged on to do more work. Even with a supportive husband. Again, maybe this isn't needed in your industry, I don't know.
3 and 4) are related to the difficulty of getting and keeping a senior position. If they don't open up frequently and need a lot of management support etc then you'd be foolish to not grab it, when it so fortuitously presents itself. On the other hand, senior roles are more prone to being measured on results, re-orgs, at higher risk of being cut during bad times.
You're only 33 and being recommended for a senior role already, on mat leave with 3 kids so you're clearly a high performer with a supportive employer. The question here is really what do you prioritise. If you want the role and are willing to put in the work, I'd say take it in a heartbeat.
If you find yourself holding back - not because of any doubts regarding your ability, adapting to change or being 'fair to employers' - but because you want to take your foot off the gas for a bit and security - that's fine too. but just make sure you pass it up for the right reasons.
I agree with people saying it might take you a while to conceive but also you currently have a baby.. so hardly unoccupied on that front.