For me it was meeting up with other mums regularly, but also, working/studying part time. I always wanted to be a SAHM and I do actually think it's the best thing and am not massively keen on nurseries for little ones (I used a childminder which I found personally better) but I just don't enjoy it anywhere near as much as I thought I would.
I thought I'd be all creative and engaged and think up fun activities every day and spend time playing and have loads of energy and never shout. The reality is just very different. Children are lovely but they are also frustrating and it can be really hard to keep your cool! I found that I really needed breaks which surprised me because I had thought that being with children all day would be a break
(not sure where that idea came from!) And I didn't give myself breaks when DS was little, because, I know this sounds stupid, I didn't really realise I was allowed to
So I would swing from being all involved to periods where I couldn't do anything and I would find it difficult to interact with him at all. I found that my lack of organisation might feel laid back, but with children, actually, you can't afford to be laid back. You have to have a measure of control and organisation to be able to be a laid back parent.
I desperately needed adult contact and I found the whole thing so much better when I got that regularly. Whether that means groups, or meeting up with friends and/or family, going to their house, having them over to yours. You need your "village". And the more adults your DC know, the more likely you are to be able to find one of those adults to babysit, even if you don't want to do that right now.
I agree with getting a cleaner - it just reduces one burden off you. Otherwise that's just another (depressing!) thing to worry about.
I also think that, even if you're not a structure person, it helps to have just a very rough structure to the day. This helps me enormously and I was so anti routine when DS was little that it took me until he was nearly 7 (!) to work it out. So you have lunch at a set time, you have your groups on certain days, perhaps you have "outdoor" time and "indoor" time, or however you want to break it up, and SO IMPORTANT: "Mummy's breaktime". It's a very good idea to introduce a time in the day, at least one or two, where you are around and available for emergencies of course, but you don't sit and play, you don't read to them, you don't show them how to do things, you just have a break. This is complete anathema to the usual doctrine about how we have to be more present, but I think that that has swung so far that we are typically trying to be "present" ALL the time, which is totally unsustainable, and then feeling guilty and worn out by it and thus less able to be present ANY of the time. So build in some time for you and know that it is okay and not anything to feel guilty about to take it. It's okay for them to learn that people need time out and that they can't always expect others to want to do the thing they want to do at the exact same time they want to do it.
And by that token - you have to be careful when you're a SAHM and especially when the DC are very little that you are not slipping into the role of "default parent" even when your DH or DP is around. That is a killer, because it puts you on duty absolutely 24/7. It's hard to be on duty all the time when DH is not at home but it's crushing to be on duty all the time even when he's there, and it will exhaust you. So not just "helping" but things like - do you feel totally able to just say "I'm popping out" at the weekend and doing so, going off for a nap, or a run, or to the supermarket. I'm not talking weekends away with such a little baby (though you could - take the baby with you) but these simple things. Who notices that it's time for dinner, who gets up in the night, who goes to DC when they are hurt, who takes them to weekend birthday parties, who does bedtime? Would your DH notice if he'd dressed them in too-small or dirty clothes which were mistakenly in the drawer and would he know what to do about it?
I also think you're in a hard age where the bigger one wants lots of entertaining and the younger one isn't old enough to play with. In six months to a year, they'll be much better able to entertain each other and you'll find things easier.
Good luck! :) Let us know how you get on.