I am feeling like I am failing...I am running out of activities to fill up our summer!

take a break! it won't kill your LO to just do nothing..8mos-preg with a toddler-in-tow is enough. besides, she/he needs to learn to occupy him/herself..you'll be plenty busy with the baby soon. not saying you'll neglect the LO, of course, just that you may be putting too much pressure on yourself.
there are no SuperMoms. take a break and enjoy this last month, just you and your LO.

Hmm...arts and crafts? Maybe a movie marathon (that'll entertain him and allow you to sit and relax)? Slip n Slide in the backyard? Neighborhood park, maybe a playdate with a friend? Maybe you could gather up a few small toys (or buy some new ones) and hide them around the house or yard and make it a scavenger hunt. Depending on where Daddy works, maybe you could take him lunch. That's all I can come up with right now.

Have you been doing the free summer movies? My 2 yo loves them - and if she only sits for an hour of it, hey it was free! You should be able to google them in your area. Sidewalk chalk, bubbles, library story time, new playgrounds. Give her a paintbrush and bucket of water and let her "paint" the deck or porch. Sprinkler in the yard?

You know you do not have to fill up their summer with activities.BUT
If you have some squirt bottles like ketchup bottles with the pointly tops you can fill them with water and let your child draw on the sidewalk with water.
You can take a lipped cookie sheet and put in a dollop or two of pudding and let her draw or for that matter on her high chair tray just smooth it out and show her how to make a circle a house and let her design. You can use two different colors if you are into swirls.
f you have some large buttons and a shoelace she can string them.
Give her a bowl in the bathtub or pool with cup and measuring spoons. A funnel is fun too.

you can play hide and seek with stuffed animals. You hide them (not too hard) and she finds them you give her a little treat for getting them all put away.

Let her help you dust the furniture. Let her help pick up the bits off the floor befor you vaccuum.

Take it easy and think smaller. When I was home with my 2 year old, some of our regular fun weekly activities included: grocery shopping, Target Day (I'd let him run around for a while and explore then give him a snack in the cart while I shopped), laundry folding day (he's ALWAYS loved playing with laundry), tons and tons of reading, watering the plants (I gave him a tiny watering can and let him try to help me, or just make a mess), baking day (cookies or muffins from a box), Subway day (lunch out with mom), etc. You can seriously fill a week with this stuff.

And if you want to get out, go to the library or parks or free days at any local museum (doesn't have to be a kid's museum). Or just go for a little walk to look at cars and talk about how traffic works (lights, cross walks, street signs, etc.)

It's not failing to not have activities planned. For starters, kids need time to just be - to do nothing. To learn how to entertain themselves at home with nothing but their imagination and maybe some of their toys. They need to learn how to fill their time on their own. It's not to say you don't plan an occasional activity or that you never play...it's just saying don't stress out or measure your success on your calendar.

As for ideas on how to fill the time? My son (now 10) turned 2 in June the year my DD was born (in September.) The summer gave us lots of time to play board games, read to together, go to Library programs, visit parks, watch movies, play in our yard, etc. We picked up a netted bug habitat and would look for caterpillar's in our yard that we could move into the habitat. We'd watch them cocoon and then emerge. After the butterfly's wings dried and they were able to flutter around, we would release them.

sometimes kids just need to play alone in their room to work on their imagination...you dont have to plan something all the time for them. let them plan their own fun.

plus you need to rest up for when that baby comes :)

If you have a yard and its hot -throw on the sprinkler. Make kool aid ice cubes(FUN!) let him play with those in the bath. have him paint sticks to make them look like snakes. Shaving cream fight, pudding finger painting(outside)Get a bubble machine,play doh crayons and paper, let him make a fort out of blankets and boxes-have him color the boxes first.G Have him collect bugs,chase butterflies.