Not sure if this would work for you, you need transport and a few garden centre with cafes...but this time of the year, until my eldest was at school, I would drive to a biggish garden centre, with lovely toilets, facilities and Christmas decs and have a wander and maybe let toddler choose one cheap ish dec if beautifully behaved (this was pre agreed!) and we would look at lights, trees outside and finish off with a drink in the cafe. One near me even used to have a lovely train set whizzing away through Christmas scenes.
You may get bored looking at gross flashing penguins etc but toddler and baby will love it.
I still have a collection of golden pine cones chosen by my toddler from those days....I would have chosen natural or silver but she loved golden ones so she decorated her room with them.
If baby is good humoured enough, how about promising time on Cbeebies app, it's really very good and promising one printable item each day. You can open their advent calendar and just print off a pic of her fav character which she can colour alone. Then help her put them up somewhere in her room/space.
I also vote for very simple Christmas theme DVDs, check out a big Asda for bargains on old classics. Mine would enjoy Snowman, Father Christmas and Thomas 's winter wonderland at that age. If toddler still drinks milk, make her a fake babychino for afternoon treat.
In my experience, of 3, simple pleasures are your toddler's best friend, it's how you present them!
I bet you are doing a great job, it is hard but this time next year the baby will be mobile and joining in so much better! Hang in there x