OK, first off you have NO reason to feel guilty, your days sound lovely. We seriously need to get out of the house here every day too or things do not go well later on in the day. My dd plays really well by herself too -- I would really just take her lead, if she needs you to read or play with her, she'll let you know. And it will be really helpful that she is so independent when #2 arrives (it was great for us).
As far as a schedule goes, maybe you could designate a certain amount of time each day to certain activities (as in 30 minutes of art activities a day, 30 minutes of outside time, 20 minutes of reading books) and fit the independent play in where it falls. There's a ton of ideas on the Toddler Activity sticky at the top of the forum that you can look at.
Really though, you sound like a wonderful mom. Don't worry so much!