Aw don't feel guilty x amazingly I was talking to a parent today at parents and tots group that felt like this so I gave her some ideas;
Ask your daughter where she'd like to go and explore each Monday and wherever she chooses you can do loads of activities based around that. For example say she wants to explore under the sea, you could make fish pictures together and peg them up in a certain room on Monday, go shell hunting (at a pound shop or if you're close enough to a beach you could go there) and make shell pictures on Tuesday, on Wednesday you could explore things that sink and float in the bath (get some blue food dye and add that) and then make your own floating boats, make jelly on Thursday for the 'jelly fish' and on Friday you could have an 'under the sea' lunch where you dress up as mermaids and eat the jelly fish, have fish cakes or fish fingers etc.
Get a box and fill it full of loads of different material off cuts, scraps etc toddlers (in fact all kids) love playing with material then you can tie it in to the place you're exploring that week (so in our example 'under the sea' using blue material for the sea, green material for mermaid tails etc etc)
Hope this helps a little. I did this with DD and will do it again with Seb when hrs older.