I think being consistant from day one with behaviour and habits as you described is a very good thing. The children SHOULD respect toys whether they are your sons or not. I am always on my dck's cases for good manners and playing appropriately. Ultimatly thats how they learn, by us consistantly telling them. Before you know it they will adopt these habits and behaviours and the frequency with which you remind them for the most will reduce. Some children may need more of these reminders if these good behaviours/habits arent reinforced at home. Its very important for the children to learn these things, so bravo to you for being consistant as they will be better kids for it in the long run.
Once your other 2 children arrive you will probably find the kiddies entertain themselves a little more independently so you can take a step back and observe the children happily playing. I think its a bit overwhelming at first when you start a daycare.Its so much busier than you first think IMO.
Make sure you schedule some "self care" time. At naptimes and also out of work hours. Its really easy to burn out in this job if you don't look after yourself. I'm sure you are doing a great job theres just a bit of an adjustment period for both the kids and yourself.