Be aware that some non-fermentable sweeteners can cause gastric issues. (e.g. pears contain moderate levels of sorbitol and that is why they have a reputation for causing "the runs" and are sometimes used as a mild laxative).
I use waterbath pasteurisation to deal with sweetened and carbonated cider. See Pappers post at the top of the forum, JimRausch 16 April 2018 or my post of 1 Feb 2021 which goes into a lot of detail. Be aware that some caution is needed to ensure that over-carbonation or temperature doesn't take you into "bottle bomb" territory. Carbonation up to about 2.5 volumes of CO2 is O.K. in my experience. Heating the sealed bottles to 65C (149F) for around 10 minutes will do the job of stopping the yeast from any further fermentation, thus leaving sugar and CO2 in the bottle.
It is a bit late for you on this occasion, but a few on the forum (including me) are trying Fermentis' new AS2 and TF6 yeasts which claim to retain some sweetness when fully fermented. I have found this to be the case with S04 which can stop between 1.002 and 1.004.
I have also used Xylitol but am concerned that it can be toxic to dogs. Others may have suggestions.