Strapons

Traditional strapons are great for beginners.  They are easier to control than a strapless one and are more affordable when just starting out.  Below are a few models to consider.  Consider a vibrating one for her pleasureI always recommend buying silicone dildos because they are the safest and easiest to clean.  Be sure to only use water-based anal lubes with them though as silicone lubes wreck silicone toys!
Strapon Sets
Simple kits will give you everything you need to get started.  Great for beginners!
Plus Size Harnesses
Not all harnesses fit every body type and most tend to fit quite small so always buy one a little bigger that adjusts down.
Harnesses
Buying the harness separate from the dildo gives you better control over what works for you as far as material and shape.
Vac-U-Lock
This system allows you to buy interchangeable dildos and harnesses that snap together for rigorous play.
Vibrating Strapons
For those of you who like a little vibration these styles are a good bet to increase pleasure for all him and her!
Hollow Strapons
For those of you who want to strapon on a little something bigger than what you've got get out these models.

Strapless Strapons

When it comes to using a strapless dildo you need to consider is how strong your pelvic floor muscles are...especially after child-bearing.  Holding it in place without actually "holding it on place" may take some work.  Luckily there are amazing toys on the market to help build the muscles up!  You will also find an increase in your ability to have g-spot orgasms as well as squirting with a little pelvic floor muscle attention.  Below are some styles of both strapless strapons and muscles building toys to get you started.  You really need to have some serious pelvic floor muscles to have full control over it's movement. 

Overall strapless toys are great because you get to enjoy the push and pull sensation internally.  Many women can actually have g-spot orgasms while using this stype of strapon on their partners.  If your muscles aren't quite up to snuff you can always harness many of the strapless styles to start.
 
 
Do you have a partner who is concerned about her size and feeling a little self conscious about being at the helm of the action?  Here are some things to consider:

1. Being on display while fucking you.  You may want to show her there are other positions that she can enjoy your ass in.  For instance, you can ride her girlcock…this puts the onus on you to be the active one.  Another is to have you on bent over the side of the bed and she can stand behind.  These may help ease her into it until she finds her confidence.

Pegging Positions
2. Strapons not fitting. - I am not sure of her size but if this is a concern, there are several plus size strapons that will adjust to fit any body size.  Here are a few:

Plus-Sized Strapons


Other than that, just encourage her to play with your ass more…perhaps she can manually fuck it with a dildo to see how hot it gets you!