My suggestion is that you try to remember the things that you loved to do with your dad… and maybe nudge your husband in the direction of those activities. Make it as easy as possible for him. It doesn’t sound like he is a natural with kids, but if you provide the inspiration and the materials; he might gain confidence as he gets to know his children better. Some suggestions:
1) Coin collecting – just get some empty coin collecting books and put “Dad” on one, and your children’s names on the others. Then get rolls of pennies from the bank. Inexpensive. I used to do this with my father. He would bring home his spare change and put it into a jar. My brothers and I would sit on the floor or at the table and sort the coins with him. As we were sorting through the coins he would tell us stories about his childhood or lecture us on various subjects. Sometimes we didn’t do much talking. We just sat close together and sorted coins. It’s one of my fondest memories of my Father.
2) Rockets. I used to love to launch toy rockets with my dad and brothers on our street & at the park.
3) Reinvigorate the family albums. Have each of your children create a family album that they will take with them when they move out or go to college. Can you get your husband’s mother to give you pictures of him in childhood? You should get some of you as a child too. Children of all ages are curious about who their parents were before they were parents. Take some new photos too.
4) Would he build the kids a backyard clubhouse or a go-cart? Maybe they could help or at least watch him build these.
5) Start a family blog or website.
6) Can he help the kids build bird feeders & bird houses? You can get a bird book so you can identify the birds that show up in your yard.
7) Perhaps your girls would enjoy baking some cookies for their dad to take to work to share with his colleagues?
8) Frame some small pictures of the kids for your husband to keep on his desk. Put photos in his wallet and on his cell phone so he can show them to people.
9) What were your husband’s favorite movies from his youth? Rent those and watch them with the kids.
10) Backyard camping.
11) Barbecue.
12) Take family hikes, or send him with just the kids, or just one kid.
13) Install a basketball hoop on the garage door & let him shoot hoops with the kids.
14) Read books out loud.
15) Have a puzzle on the kitchen table that everyone can work on together.
16) Board games, cards, chess.
17) When the weather gets colder, take a trip up to the snow and go sledding with the kids.
Perhaps some of these resonate as activities your husband would enjoy doing with the kiddos. Best of luck!
P.S. On another note, you might find this directory of services for children with disabilities useful:
www.yellowpagesforkids.com